Jeremiah Lowin Claude commited on
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Update client docs

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Co-Authored-By: Claude <claude@users.noreply.github.com>

docs/clients/advanced-features.mdx DELETED
@@ -1,152 +0,0 @@
1
- ---
2
- title: Advanced Features
3
- sidebarTitle: Advanced Features
4
- description: Learn about the advanced features of the FastMCP Client.
5
- icon: stars
6
- ---
7
-
8
- import { VersionBadge } from '/snippets/version-badge.mdx'
9
-
10
- In addition to basic server interaction, FastMCP clients can also handle more advanced features and server interaction patterns. The `Client` constructor accepts additional configuration to handle these server requests.
11
-
12
- <Tip>
13
- To enable many of these features, you must provide an appropriate handler or callback function. For example. In most cases, if you do not provide a handler, FastMCP's default handler will emit a `DEBUG` level log.
14
- </Tip>
15
-
16
- ## Logging and Notifications
17
-
18
- <VersionBadge version="2.0.0" />
19
- MCP servers can emit logs to clients. To process these logs, you can provide a `log_handler` to the client.
20
-
21
- The `log_handler` must be an async function that accepts a single argument, which is an instance of `fastmcp.client.logging.LogMessage`. This has attributes like `level`, `logger`, and `data`.
22
-
23
- ```python {2, 12}
24
- from fastmcp import Client
25
- from fastmcp.client.logging import LogMessage
26
-
27
- async def log_handler(message: LogMessage):
28
- level = message.level.upper()
29
- logger = message.logger or 'default'
30
- data = message.data
31
- print(f"[Server Log - {level}] {logger}: {data}")
32
-
33
- client_with_logging = Client(
34
- ...,
35
- log_handler=log_handler,
36
- )
37
- ```
38
- ## Progress Monitoring
39
-
40
- <VersionBadge version="2.3.5" />
41
-
42
- MCP servers can report progress during long-running operations. The client can set a progress handler to receive and process these updates.
43
-
44
- ```python {2, 13}
45
- from fastmcp import Client
46
- from fastmcp.client.progress import ProgressHandler
47
-
48
- async def my_progress_handler(
49
- progress: float,
50
- total: float | None,
51
- message: str | None
52
- ) -> None:
53
- print(f"Progress: {progress} / {total} ({message})")
54
-
55
- client = Client(
56
- ...,
57
- progress_handler=my_progress_handler
58
- )
59
- ```
60
-
61
- By default, FastMCP uses a handler that logs progress updates at the debug level. This default handler properly handles cases where `total` or `message` might be None.
62
-
63
- You can override the progress handler for specific tool calls:
64
-
65
- ```python
66
- # Client uses the default debug logger for progress
67
- client = Client(...)
68
-
69
- async with client:
70
- # Use default progress handler (debug logging)
71
- result1 = await client.call_tool("long_task", {"param": "value"})
72
-
73
- # Override with custom progress handler just for this call
74
- result2 = await client.call_tool(
75
- "another_task",
76
- {"param": "value"},
77
- progress_handler=my_progress_handler
78
- )
79
- ```
80
-
81
- A typical progress update includes:
82
- - Current progress value (e.g., 2 of 5 steps completed)
83
- - Total expected value (may be None)
84
- - Status message (may be None)
85
-
86
- ## LLM Sampling
87
-
88
- <VersionBadge version="2.0.0" />
89
-
90
- MCP Servers can request LLM completions from clients. The client can provide a `sampling_handler` to handle these requests. The sampling handler receives a list of messages and other parameters from the server, and should return a string completion.
91
-
92
- The following example uses the `marvin` library to generate a completion:
93
-
94
- ```python {8-17, 21}
95
- import marvin
96
- from fastmcp import Client
97
- from fastmcp.client.sampling import (
98
- SamplingMessage,
99
- SamplingParams,
100
- RequestContext,
101
- )
102
-
103
- async def sampling_handler(
104
- messages: list[SamplingMessage],
105
- params: SamplingParams,
106
- context: RequestContext
107
- ) -> str:
108
- return await marvin.say_async(
109
- message=[m.content.text for m in messages],
110
- instructions=params.systemPrompt,
111
- )
112
-
113
- client = Client(
114
- ...,
115
- sampling_handler=sampling_handler,
116
- )
117
- ```
118
-
119
-
120
- ## Roots
121
-
122
- <VersionBadge version="2.0.0" />
123
-
124
- Roots are a way for clients to inform servers about the resources they have access to or certain boundaries on their access. The server can use this information to adjust behavior or provide more accurate responses.
125
-
126
- Servers can request roots from clients, and clients can notify servers when their roots change.
127
-
128
- To set the roots when creating a client, users can either provide a list of roots (which can be a list of strings) or an async function that returns a list of roots.
129
-
130
- <CodeGroup>
131
- ```python Static Roots {5}
132
- from fastmcp import Client
133
-
134
- client = Client(
135
- ...,
136
- roots=["/path/to/root1", "/path/to/root2"],
137
- )
138
- ```
139
- ```python Dynamic Roots Callback {4-6, 10}
140
- from fastmcp import Client
141
- from fastmcp.client.roots import RequestContext
142
-
143
- async def roots_callback(context: RequestContext) -> list[str]:
144
- print(f"Server requested roots (Request ID: {context.request_id})")
145
- return ["/path/to/root1", "/path/to/root2"]
146
-
147
- client = Client(
148
- ...,
149
- roots=roots_callback,
150
- )
151
- ```
152
- </CodeGroup>
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
docs/clients/client.mdx CHANGED
@@ -1,7 +1,7 @@
1
  ---
2
  title: Client Overview
3
  sidebarTitle: Overview
4
- description: Learn how to use the FastMCP Client to interact with MCP servers.
5
  icon: user-robot
6
  ---
7
 
@@ -9,388 +9,198 @@ import { VersionBadge } from '/snippets/version-badge.mdx'
9
 
10
  <VersionBadge version="2.0.0" />
11
 
12
- The `fastmcp.Client` provides a high-level, asynchronous interface for interacting with any Model Context Protocol (MCP) server, whether it's built with FastMCP or another implementation. It simplifies communication by handling protocol details and connection management.
13
 
14
- ## FastMCP Client
 
 
15
 
16
- The FastMCP Client architecture separates the protocol logic (`Client`) from the connection mechanism (`Transport`).
17
 
18
- - **`Client`**: Handles sending MCP requests (like `tools/call`, `resources/read`), receiving responses, and managing callbacks.
19
- - **`Transport`**: Responsible for establishing and maintaining the connection to the server (e.g., via WebSockets, SSE, Stdio, or in-memory).
20
-
21
- ### Transports
22
-
23
- Clients must be initialized with a `transport`. You can either provide an already instantiated transport object, or provide a transport source and let FastMCP attempt to infer the correct transport to use.
24
 
25
- The following inference rules are used to determine the appropriate `ClientTransport` based on the input type:
26
 
27
- 1. **`ClientTransport` Instance**: If you provide an already instantiated transport object, it's used directly.
28
- 2. **`FastMCP` Instance**: Creates a `FastMCPTransport` for efficient in-memory communication (ideal for testing). This also works with a **FastMCP 1.0 server** created via `mcp.server.fastmcp.FastMCP`.
29
- 3. **`Path` or `str` pointing to an existing file**:
30
- * If it ends with `.py`: Creates a `PythonStdioTransport` to run the script using `python`.
31
- * If it ends with `.js`: Creates a `NodeStdioTransport` to run the script using `node`.
32
- 4. **`AnyUrl` or `str` pointing to a URL that begins with `http://` or `https://`**:
33
- * Creates a `StreamableHttpTransport`
34
- 5. **`MCPConfig` or dictionary matching MCPConfig schema**: Creates a client that connects to one or more MCP servers specified in the config.
35
- 6. **Other**: Raises a `ValueError` if the type cannot be inferred.
36
 
37
  ```python
38
  import asyncio
39
  from fastmcp import Client, FastMCP
40
 
41
- # Example transports (more details in Transports page)
42
- server_instance = FastMCP(name="TestServer") # In-memory server
43
- http_url = "https://example.com/mcp" # HTTP server URL
44
- server_script = "my_mcp_server.py" # Path to a Python server file
45
 
46
- # Client automatically infers the transport type
47
- client_in_memory = Client(server_instance)
48
- client_http = Client(http_url)
49
 
50
- client_stdio = Client(server_script)
 
51
 
52
- print(client_in_memory.transport)
53
- print(client_http.transport)
54
- print(client_stdio.transport)
 
 
 
 
 
 
 
 
 
 
55
 
56
- # Expected Output (types may vary slightly based on environment):
57
- # <FastMCP(server='TestServer')>
58
- # <StreamableHttp(url='https://example.com/mcp')>
59
- # <PythonStdioTransport(command='python', args=['/path/to/your/my_mcp_server.py'])>
60
  ```
61
 
62
- You can also initialize a client from an MCP configuration dictionary or `MCPConfig` file:
63
 
64
- ```python
65
- from fastmcp import Client
66
 
67
- config = {
68
- "mcpServers": {
69
- "local": {"command": "python", "args": ["local_server.py"]},
70
- "remote": {"url": "https://example.com/mcp"},
71
- }
72
- }
73
 
74
- client_config = Client(config)
 
 
 
 
 
 
 
 
 
 
 
 
75
  ```
 
76
  <Tip>
77
- For more control over connection details (like headers for SSE, environment variables for Stdio), you can instantiate the specific `ClientTransport` class yourself and pass it to the `Client`. See the [Transports](/clients/transports) page for details.
78
  </Tip>
79
 
80
- ### Multi-Server Clients
81
 
82
  <VersionBadge version="2.4.0" />
83
 
84
- FastMCP supports creating clients that connect to multiple MCP servers through a single client interface using a standard MCP configuration format (`MCPConfig`). This configuration approach makes it easy to connect to multiple specialized servers or create composable systems with a simple, declarative syntax.
85
-
86
- <Note>
87
- The MCP configuration format follows an emerging standard and may evolve as the specification matures. FastMCP will strive to maintain compatibility with future versions, but be aware that field names or structure might change.
88
- </Note>
89
-
90
- When you create a client with an `MCPConfig` containing multiple servers:
91
-
92
- 1. FastMCP creates a composite client that internally mounts all servers using their config names as prefixes
93
- 2. Tools and resources from each server are accessible with appropriate prefixes in the format `servername_toolname` and `protocol://servername/resource/path`
94
- 3. You interact with this as a single unified client, with requests automatically routed to the appropriate server
95
 
96
  ```python
97
- from fastmcp import Client
98
-
99
- # Create a standard MCP configuration with multiple servers
100
  config = {
101
  "mcpServers": {
102
- # A remote HTTP server
103
- "weather": {
104
- "url": "https://weather-api.example.com/mcp",
105
- "transport": "streamable-http"
106
- },
107
- # A local server running via stdio
108
- "assistant": {
109
- "command": "python",
110
- "args": ["./my_assistant_server.py"],
111
- "env": {"DEBUG": "true"}
112
- }
113
  }
114
  }
115
 
116
- # Create a client that connects to both servers
117
  client = Client(config)
118
 
119
- async def main():
120
- async with client:
121
- # Access tools from different servers with prefixes
122
- weather_data = await client.call_tool("weather_get_forecast", {"city": "London"})
123
- response = await client.call_tool("assistant_answer_question", {"question": "What's the capital of France?"})
124
-
125
- # Access resources with prefixed URIs
126
- weather_icons = await client.read_resource("weather://weather/icons/sunny")
127
- templates = await client.read_resource("resource://assistant/templates/list")
128
-
129
- print(f"Weather: {weather_data}")
130
- print(f"Assistant: {response}")
131
-
132
- if __name__ == "__main__":
133
- asyncio.run(main())
134
  ```
135
 
136
- If your configuration has only a single server, FastMCP will create a direct client to that server without any prefixing.
137
 
138
- ## Client Usage
139
-
140
- ### Connection Lifecycle
141
-
142
- The client operates asynchronously and must be used within an `async with` block. This context manager handles establishing the connection, initializing the MCP session, and cleaning up resources upon exit.
143
 
144
  ```python
145
- import asyncio
146
- from fastmcp import Client
147
-
148
- client = Client("my_mcp_server.py") # Assumes my_mcp_server.py exists
149
-
150
- async def main():
151
- # Connection is established here
152
  async with client:
153
- print(f"Client connected: {client.is_connected()}")
154
-
155
- # Make MCP calls within the context
156
  tools = await client.list_tools()
157
- print(f"Available tools: {tools}")
158
-
159
- if any(tool.name == "greet" for tool in tools):
160
- result = await client.call_tool("greet", {"name": "World"})
161
- print(f"Greet result: {result}")
162
-
163
- # Connection is closed automatically here
164
- print(f"Client connected: {client.is_connected()}")
165
-
166
- if __name__ == "__main__":
167
- asyncio.run(main())
168
  ```
169
 
170
- You can make multiple calls to the server within the same `async with` block using the established session.
171
-
172
- ### Client Methods
173
 
174
- The `Client` provides methods corresponding to standard MCP requests:
175
 
176
- <Warning>
177
- The standard client methods return user-friendly representations that may change as the protocol evolves. For consistent access to the complete data structure, use the `*_mcp` methods described later.
178
- </Warning>
 
 
 
179
 
180
- #### Tool Operations
181
 
182
- * **`list_tools()`**: Retrieves a list of tools available on the server.
183
- ```python
 
184
  tools = await client.list_tools()
185
- # tools -> list[mcp.types.Tool]
186
- ```
187
- * **`call_tool(name: str, arguments: dict[str, Any] | None = None, timeout: float | None = None, progress_handler: ProgressHandler | None = None)`**: Executes a tool on the server.
188
- ```python
189
- result = await client.call_tool("add", {"a": 5, "b": 3})
190
- # result -> list[mcp.types.TextContent | mcp.types.ImageContent | ...]
191
- print(result[0].text) # Assuming TextContent, e.g., '8'
192
 
193
- # With timeout (aborts if execution takes longer than 2 seconds)
194
- result = await client.call_tool("long_running_task", {"param": "value"}, timeout=2.0)
195
-
196
- # With progress handler (to track execution progress)
197
- result = await client.call_tool(
198
- "long_running_task",
199
- {"param": "value"},
200
- progress_handler=my_progress_handler
201
- )
202
- ```
203
- * Arguments are passed as a dictionary. FastMCP servers automatically handle JSON string parsing for complex types if needed.
204
- * Returns a list of content objects (usually `TextContent` or `ImageContent`).
205
- * The optional `timeout` parameter limits the maximum execution time (in seconds) for this specific call, overriding any client-level timeout.
206
- * The optional `progress_handler` parameter receives progress updates during execution, overriding any client-level progress handler.
207
-
208
- #### Resource Operations
209
-
210
- * **`list_resources()`**: Retrieves a list of static resources.
211
- ```python
212
  resources = await client.list_resources()
213
- # resources -> list[mcp.types.Resource]
214
- ```
215
- * **`list_resource_templates()`**: Retrieves a list of resource templates.
216
- ```python
217
- templates = await client.list_resource_templates()
218
- # templates -> list[mcp.types.ResourceTemplate]
219
- ```
220
- * **`read_resource(uri: str | AnyUrl)`**: Reads the content of a resource or a resolved template.
221
- ```python
222
- # Read a static resource
223
- readme_content = await client.read_resource("file:///path/to/README.md")
224
- # readme_content -> list[mcp.types.TextResourceContents | mcp.types.BlobResourceContents]
225
- print(readme_content[0].text) # Assuming text
226
-
227
- # Read a resource generated from a template
228
- weather_content = await client.read_resource("data://weather/london")
229
- print(weather_content[0].text) # Assuming text JSON
230
- ```
231
-
232
- #### Prompt Operations
233
-
234
- * **`list_prompts()`**: Retrieves available prompt templates.
235
- * **`get_prompt(name: str, arguments: dict[str, Any] | None = None)`**: Retrieves a rendered prompt message list.
236
-
237
- <VersionBadge version="2.9.0" />
238
-
239
- **Automatic Argument Serialization**: When calling prompts with complex arguments, the FastMCP client automatically serializes non-string values to JSON strings as required by the MCP specification. This allows you to pass typed objects directly while maintaining protocol compliance.
240
-
241
- ```python
242
- from dataclasses import dataclass
243
-
244
- @dataclass
245
- class UserData:
246
- name: str
247
- age: int
248
-
249
- async with client:
250
- # You can pass complex objects directly
251
- result = await client.get_prompt("analyze_user", {
252
- "user": UserData(name="Alice", age=30), # Automatically serialized to JSON
253
- "preferences": {"theme": "dark"}, # Dict serialized to JSON string
254
- "scores": [85, 92, 78], # List serialized to JSON string
255
- "simple_name": "Bob" # Strings passed through unchanged
256
- })
257
- ```
258
-
259
- The client handles the serialization automatically using `pydantic_core.to_json()` for consistent formatting, while the server can deserialize these JSON strings back to the expected types if using FastMCP's server-side type conversion.
260
-
261
- ### Raw MCP Protocol Objects
262
-
263
- <VersionBadge version="2.2.7" />
264
-
265
- The FastMCP client attempts to provide a "friendly" interface to the MCP protocol, but sometimes you may need access to the raw MCP protocol objects. Each of the main client methods that returns data has a corresponding `*_mcp` method that returns the raw MCP protocol objects directly.
266
-
267
- <Warning>
268
- The standard client methods (without `_mcp`) return user-friendly representations of MCP data, while `*_mcp` methods will always return the complete MCP protocol objects. As the protocol evolves, changes to these user-friendly representations may occur and could potentially be breaking. If you need consistent, stable access to the full data structure, prefer using the `*_mcp` methods.
269
- </Warning>
270
-
271
- ```python
272
- # Standard method - returns just the list of tools
273
- tools = await client.list_tools()
274
- # tools -> list[mcp.types.Tool]
275
-
276
- # Raw MCP method - returns the full protocol object
277
- result = await client.list_tools_mcp()
278
- # result -> mcp.types.ListToolsResult
279
- tools = result.tools
280
  ```
281
 
282
- Available raw MCP methods:
283
-
284
- * **`list_tools_mcp()`**: Returns `mcp.types.ListToolsResult`
285
- * **`call_tool_mcp(name, arguments)`**: Returns `mcp.types.CallToolResult`
286
- * **`list_resources_mcp()`**: Returns `mcp.types.ListResourcesResult`
287
- * **`list_resource_templates_mcp()`**: Returns `mcp.types.ListResourceTemplatesResult`
288
- * **`read_resource_mcp(uri)`**: Returns `mcp.types.ReadResourceResult`
289
- * **`list_prompts_mcp()`**: Returns `mcp.types.ListPromptsResult`
290
- * **`get_prompt_mcp(name, arguments)`**: Returns `mcp.types.GetPromptResult`
291
- * **`complete_mcp(ref, argument)`**: Returns `mcp.types.CompleteResult`
292
-
293
- These methods are especially useful for debugging or when you need to access metadata or fields that aren't exposed by the simplified methods.
294
-
295
- ### Additional Features
296
-
297
- #### Pinging the Server
298
 
299
- The client can be used to ping the server to verify connectivity.
300
-
301
- ```python
302
- async with client:
303
- await client.ping()
304
- print("Server is reachable")
305
- ```
306
-
307
- #### Session Management
308
-
309
- When using stdio transports, clients support a `keep_alive` feature (enabled by default) that maintains subprocess sessions between connection contexts. You can manually control this behavior using the client's `close()` method.
310
-
311
- When `keep_alive=False`, the client will automatically close the session when the context manager exits.
312
 
313
  ```python
314
  from fastmcp import Client
 
315
 
316
- client = Client("my_mcp_server.py") # keep_alive=True by default
317
-
318
- async def example():
319
- async with client:
320
- await client.ping()
321
-
322
- async with client:
323
- await client.ping() # Same subprocess as above
324
- ```
325
-
326
- <Note>
327
- For detailed examples and configuration options, see [Session Management in Transports](/clients/transports#session-management).
328
- </Note>
329
-
330
- #### Timeouts
331
-
332
- <VersionBadge version="2.3.4" />
333
 
334
- You can control request timeouts at both the client level and individual request level:
 
335
 
336
- ```python
337
- from fastmcp import Client
338
- from fastmcp.exceptions import McpError
339
-
340
- # Client with a global 5-second timeout for all requests
341
  client = Client(
342
- my_mcp_server,
343
- timeout=5.0 # Default timeout in seconds
 
 
344
  )
345
-
346
- async with client:
347
- # This uses the global 5-second timeout
348
- result1 = await client.call_tool("quick_task", {"param": "value"})
349
-
350
- # This specifies a 10-second timeout for this specific call
351
- result2 = await client.call_tool("slow_task", {"param": "value"}, timeout=10.0)
352
-
353
- try:
354
- # This will likely timeout
355
- result3 = await client.call_tool("medium_task", {"param": "value"}, timeout=0.01)
356
- except McpError as e:
357
- # Handle timeout error
358
- print(f"The task timed out: {e}")
359
  ```
360
 
361
- <Warning>
362
- Timeout behavior varies between transport types:
363
 
364
- - With **SSE** transport, the per-request (tool call) timeout **always** takes precedence, regardless of which is lower.
365
- - With **HTTP** transport, the **lower** of the two timeouts (client or tool call) takes precedence.
366
 
367
- For consistent behavior across all transports, we recommend explicitly setting timeouts at the individual tool call level when needed, rather than relying on client-level timeouts.
368
- </Warning>
 
 
369
 
370
- #### Error Handling
 
 
 
 
371
 
372
- When a `call_tool` request results in an error on the server (e.g., the tool function raised an exception), the `client.call_tool()` method will raise a `fastmcp.exceptions.ClientError`.
373
-
374
- ```python
375
- async def safe_call_tool():
376
- async with client:
377
- try:
378
- # Assume 'divide' tool exists and might raise ZeroDivisionError
379
- result = await client.call_tool("divide", {"a": 10, "b": 0})
380
- print(f"Result: {result}")
381
- except ClientError as e:
382
- print(f"Tool call failed: {e}")
383
- except ConnectionError as e:
384
- print(f"Connection failed: {e}")
385
- except Exception as e:
386
- print(f"An unexpected error occurred: {e}")
387
-
388
- # Example Output if division by zero occurs:
389
- # Tool call failed: Division by zero is not allowed.
390
- ```
391
-
392
- Other errors, like connection failures, will raise standard Python exceptions (e.g., `ConnectionError`, `TimeoutError`).
393
 
394
  <Tip>
395
- The client transport often has its own error-handling mechanisms, so you can not always trap errors like those raised by `call_tool` outside of the `async with` block. Instead, you can use `call_tool_mcp()` to get the raw `mcp.types.CallToolResult` object and handle errors yourself by checking its `isError` attribute.
396
- </Tip>
 
1
  ---
2
  title: Client Overview
3
  sidebarTitle: Overview
4
+ description: Learn how to use the FastMCP Client to programmatically interact with MCP servers.
5
  icon: user-robot
6
  ---
7
 
 
9
 
10
  <VersionBadge version="2.0.0" />
11
 
12
+ The `fastmcp.Client` is a **programmatic client** for interacting with any Model Context Protocol (MCP) server. It provides a high-level, well-typed, Pythonic interface for deterministic MCP access, making it ideal for:
13
 
14
+ - **Testing MCP servers** during development
15
+ - **Building deterministic applications** that need reliable MCP interactions
16
+ - **Creating the foundation for agentic or LLM-based clients** with structured, type-safe operations
17
 
18
+ All client operations require using the `async with` context manager for proper connection lifecycle management.
19
 
20
+ <Note>
21
+ This is not an agentic client - it requires explicit function calls and provides direct control over all MCP operations. Use it as a building block for higher-level systems.
22
+ </Note>
 
 
 
23
 
24
+ ## Quick Start
25
 
26
+ The client uses transport inference to automatically determine the connection method:
 
 
 
 
 
 
 
 
27
 
28
  ```python
29
  import asyncio
30
  from fastmcp import Client, FastMCP
31
 
32
+ # In-memory server (ideal for testing)
33
+ server = FastMCP("TestServer")
34
+ client = Client(server)
 
35
 
36
+ # HTTP server
37
+ client = Client("https://example.com/mcp")
 
38
 
39
+ # Local Python script
40
+ client = Client("my_mcp_server.py")
41
 
42
+ async def main():
43
+ async with client:
44
+ # Basic server interaction
45
+ await client.ping()
46
+
47
+ # List available operations
48
+ tools = await client.list_tools()
49
+ resources = await client.list_resources()
50
+ prompts = await client.list_prompts()
51
+
52
+ # Execute operations
53
+ result = await client.call_tool("example_tool", {"param": "value"})
54
+ print(result)
55
 
56
+ asyncio.run(main())
 
 
 
57
  ```
58
 
59
+ ## Client-Transport Architecture
60
 
61
+ The FastMCP Client separates concerns between protocol and connection:
 
62
 
63
+ - **`Client`**: Handles MCP protocol operations (tools, resources, prompts) and manages callbacks
64
+ - **`Transport`**: Establishes and maintains the connection (WebSockets, HTTP, Stdio, in-memory)
65
+
66
+ ### Transport Inference
67
+
68
+ The client automatically infers the appropriate transport based on the input:
69
 
70
+ 1. **`FastMCP` instance** → In-memory transport (perfect for testing)
71
+ 2. **File path ending in `.py`** → Python Stdio transport
72
+ 3. **File path ending in `.js`** → Node.js Stdio transport
73
+ 4. **URL starting with `http://` or `https://`** → HTTP transport
74
+ 5. **`MCPConfig` dictionary** → Multi-server client
75
+
76
+ ```python
77
+ from fastmcp import Client, FastMCP
78
+
79
+ # Examples of transport inference
80
+ client_memory = Client(FastMCP("TestServer"))
81
+ client_script = Client("./server.py")
82
+ client_http = Client("https://api.example.com/mcp")
83
  ```
84
+
85
  <Tip>
86
+ For testing and development, always prefer the in-memory transport by passing a `FastMCP` server directly to the client. This eliminates network complexity and separate processes.
87
  </Tip>
88
 
89
+ ## Multi-Server Clients
90
 
91
  <VersionBadge version="2.4.0" />
92
 
93
+ Connect to multiple MCP servers through a single client using MCP configuration:
 
 
 
 
 
 
 
 
 
 
94
 
95
  ```python
 
 
 
96
  config = {
97
  "mcpServers": {
98
+ "weather": {"url": "https://weather-api.example.com/mcp"},
99
+ "assistant": {"command": "python", "args": ["./assistant_server.py"]}
 
 
 
 
 
 
 
 
 
100
  }
101
  }
102
 
 
103
  client = Client(config)
104
 
105
+ async with client:
106
+ # Tools are prefixed with server names
107
+ weather_data = await client.call_tool("weather_get_forecast", {"city": "London"})
108
+ response = await client.call_tool("assistant_answer_question", {"question": "What's the capital of France?"})
109
+
110
+ # Resources use prefixed URIs
111
+ icons = await client.read_resource("weather://weather/icons/sunny")
112
+ templates = await client.read_resource("resource://assistant/templates/list")
 
 
 
 
 
 
 
113
  ```
114
 
115
+ ## Connection Lifecycle
116
 
117
+ The client operates asynchronously and uses context managers for connection management:
 
 
 
 
118
 
119
  ```python
120
+ async def example():
121
+ client = Client("my_mcp_server.py")
122
+
123
+ # Connection established here
 
 
 
124
  async with client:
125
+ print(f"Connected: {client.is_connected()}")
126
+
127
+ # Make multiple calls within the same session
128
  tools = await client.list_tools()
129
+ result = await client.call_tool("greet", {"name": "World"})
130
+
131
+ # Connection closed automatically here
132
+ print(f"Connected: {client.is_connected()}")
 
 
 
 
 
 
 
133
  ```
134
 
135
+ ## Core Operations
 
 
136
 
137
+ The client provides methods for all standard MCP operations:
138
 
139
+ | Operation | Method | Description |
140
+ |-----------|--------|-------------|
141
+ | **Tools** | `list_tools()`, `call_tool()` | Execute server-side functions |
142
+ | **Resources** | `list_resources()`, `read_resource()` | Access server data sources |
143
+ | **Prompts** | `list_prompts()`, `get_prompt()` | Retrieve message templates |
144
+ | **Utility** | `ping()` | Test server connectivity |
145
 
146
+ ### Quick Examples
147
 
148
+ ```python
149
+ async with client:
150
+ # Tool operations
151
  tools = await client.list_tools()
152
+ result = await client.call_tool("calculate", {"a": 5, "b": 3})
 
 
 
 
 
 
153
 
154
+ # Resource operations
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
155
  resources = await client.list_resources()
156
+ content = await client.read_resource("file:///config/settings.json")
157
+
158
+ # Prompt operations
159
+ prompts = await client.list_prompts()
160
+ messages = await client.get_prompt("welcome", {"name": "Alice"})
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
161
  ```
162
 
163
+ ## Advanced Configuration
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
164
 
165
+ The client supports additional configuration for specialized use cases:
 
 
 
 
 
 
 
 
 
 
 
 
166
 
167
  ```python
168
  from fastmcp import Client
169
+ from fastmcp.client.logging import LogMessage
170
 
171
+ async def log_handler(message: LogMessage):
172
+ print(f"Server log: {message.data}")
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
173
 
174
+ async def progress_handler(progress: float, total: float | None, message: str | None):
175
+ print(f"Progress: {progress}/{total} - {message}")
176
 
 
 
 
 
 
177
  client = Client(
178
+ "my_mcp_server.py",
179
+ log_handler=log_handler, # Handle server logs
180
+ progress_handler=progress_handler, # Monitor long operations
181
+ timeout=30.0 # Set request timeout
182
  )
 
 
 
 
 
 
 
 
 
 
 
 
 
 
183
  ```
184
 
185
+ ## Next Steps
 
186
 
187
+ Explore the detailed documentation for each operation type:
 
188
 
189
+ ### Core Interactions
190
+ - **[Tools](/clients/tools)** - Execute server-side functions and handle results
191
+ - **[Resources](/clients/resources)** - Access static and templated resources
192
+ - **[Prompts](/clients/prompts)** - Work with message templates and argument serialization
193
 
194
+ ### Advanced Features
195
+ - **[Logging](/clients/logging)** - Handle server log messages
196
+ - **[Progress](/clients/progress)** - Monitor long-running operations
197
+ - **[Sampling](/clients/sampling)** - Respond to server LLM requests
198
+ - **[Roots](/clients/roots)** - Provide local context to servers
199
 
200
+ ### Connection Details
201
+ - **[Transports](/clients/transports)** - Configure connection methods and parameters
202
+ - **[Authentication](/clients/auth/oauth)** - Set up OAuth and bearer token authentication
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
203
 
204
  <Tip>
205
+ The FastMCP Client is designed as a foundational tool. Use it directly for deterministic operations, or build higher-level agentic systems on top of its reliable, type-safe interface.
206
+ </Tip>
docs/clients/logging.mdx ADDED
@@ -0,0 +1,63 @@
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
+ ---
2
+ title: Server Logging
3
+ sidebarTitle: Logging
4
+ description: Learn how to receive and handle log messages from MCP servers.
5
+ icon: file-text
6
+ ---
7
+
8
+ import { VersionBadge } from '/snippets/version-badge.mdx'
9
+
10
+ <VersionBadge version="2.0.0" />
11
+
12
+ MCP servers can emit log messages to clients. The client can handle these logs through a log handler callback.
13
+
14
+ ## Setting Up Log Handling
15
+
16
+ Provide a `log_handler` function when creating the client:
17
+
18
+ ```python
19
+ from fastmcp import Client
20
+ from fastmcp.client.logging import LogMessage
21
+
22
+ async def log_handler(message: LogMessage):
23
+ level = message.level.upper()
24
+ logger = message.logger or 'server'
25
+ data = message.data
26
+ print(f"[{level}] {logger}: {data}")
27
+
28
+ client = Client(
29
+ "my_mcp_server.py",
30
+ log_handler=log_handler,
31
+ )
32
+ ```
33
+
34
+ ## LogMessage Structure
35
+
36
+ The `log_handler` receives a `LogMessage` object with:
37
+
38
+ - **`level`**: Log level (e.g., "debug", "info", "warning", "error")
39
+ - **`logger`**: Logger name (optional, may be None)
40
+ - **`data`**: The actual log message content
41
+
42
+ ```python
43
+ async def detailed_log_handler(message: LogMessage):
44
+ if message.level == "error":
45
+ print(f"ERROR: {message.data}")
46
+ elif message.level == "warning":
47
+ print(f"WARNING: {message.data}")
48
+ else:
49
+ print(f"{message.level.upper()}: {message.data}")
50
+ ```
51
+
52
+ ## Default Log Handling
53
+
54
+ If you don't provide a custom `log_handler`, FastMCP uses a default handler that emits DEBUG level logs:
55
+
56
+ ```python
57
+ # Without custom handler - uses default DEBUG logging
58
+ client = Client("my_mcp_server.py")
59
+
60
+ async with client:
61
+ # Server logs will be emitted at DEBUG level
62
+ await client.call_tool("some_tool")
63
+ ```
docs/clients/progress.mdx ADDED
@@ -0,0 +1,59 @@
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
+ ---
2
+ title: Progress Monitoring
3
+ sidebarTitle: Progress
4
+ description: Learn how to handle progress notifications from long-running server operations.
5
+ icon: chart-line
6
+ ---
7
+
8
+ import { VersionBadge } from '/snippets/version-badge.mdx'
9
+
10
+ <VersionBadge version="2.3.5" />
11
+
12
+ MCP servers can report progress during long-running operations. The client can receive these updates through a progress handler.
13
+
14
+ ## Setting Up Progress Handling
15
+
16
+ Set a progress handler when creating the client:
17
+
18
+ ```python
19
+ from fastmcp import Client
20
+
21
+ async def my_progress_handler(
22
+ progress: float,
23
+ total: float | None,
24
+ message: str | None
25
+ ) -> None:
26
+ if total is not None:
27
+ percentage = (progress / total) * 100
28
+ print(f"Progress: {percentage:.1f}% - {message or ''}")
29
+ else:
30
+ print(f"Progress: {progress} - {message or ''}")
31
+
32
+ client = Client(
33
+ "my_mcp_server.py",
34
+ progress_handler=my_progress_handler
35
+ )
36
+ ```
37
+
38
+ ## Per-Call Progress Handler
39
+
40
+ Override the progress handler for specific tool calls:
41
+
42
+ ```python
43
+ async with client:
44
+ # Override with specific progress handler for this call
45
+ result = await client.call_tool(
46
+ "long_running_task",
47
+ {"param": "value"},
48
+ progress_handler=my_progress_handler
49
+ )
50
+ ```
51
+
52
+ ## Handler Parameters
53
+
54
+ The progress handler receives:
55
+
56
+ - **`progress`** (float): Current progress value
57
+ - **`total`** (float | None): Expected total value (may be None)
58
+ - **`message`** (str | None): Optional status message (may be None)
59
+
docs/clients/prompts.mdx ADDED
@@ -0,0 +1,187 @@
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
+ ---
2
+ title: Prompt Operations
3
+ sidebarTitle: Prompts
4
+ description: Learn how to list and use server-side prompts with automatic argument serialization.
5
+ icon: message-square
6
+ ---
7
+
8
+ import { VersionBadge } from '/snippets/version-badge.mdx'
9
+
10
+ <VersionBadge version="2.0.0" />
11
+
12
+ Prompts are reusable message templates exposed by MCP servers. They can accept arguments to generate personalized message sequences for LLM interactions.
13
+
14
+ ## Listing Prompts
15
+
16
+ Use `list_prompts()` to retrieve all available prompt templates:
17
+
18
+ ```python
19
+ async with client:
20
+ prompts = await client.list_prompts()
21
+ # prompts -> list[mcp.types.Prompt]
22
+
23
+ for prompt in prompts:
24
+ print(f"Prompt: {prompt.name}")
25
+ print(f"Description: {prompt.description}")
26
+ if prompt.arguments:
27
+ print(f"Arguments: {[arg.name for arg in prompt.arguments]}")
28
+ ```
29
+
30
+ ## Using Prompts
31
+
32
+ ### Basic Usage
33
+
34
+ Request a rendered prompt using `get_prompt()` with the prompt name and arguments:
35
+
36
+ ```python
37
+ async with client:
38
+ # Simple prompt without arguments
39
+ result = await client.get_prompt("welcome_message")
40
+ # result -> mcp.types.GetPromptResult
41
+
42
+ # Access the generated messages
43
+ for message in result.messages:
44
+ print(f"Role: {message.role}")
45
+ print(f"Content: {message.content}")
46
+ ```
47
+
48
+ ### Prompts with Arguments
49
+
50
+ Pass arguments as a dictionary to customize the prompt:
51
+
52
+ ```python
53
+ async with client:
54
+ # Prompt with simple arguments
55
+ result = await client.get_prompt("user_greeting", {
56
+ "name": "Alice",
57
+ "role": "administrator"
58
+ })
59
+
60
+ # Access the personalized messages
61
+ for message in result.messages:
62
+ print(f"Generated message: {message.content}")
63
+ ```
64
+
65
+ ## Automatic Argument Serialization
66
+
67
+ <VersionBadge version="2.9.0" />
68
+
69
+ FastMCP automatically serializes complex arguments to JSON strings as required by the MCP specification. This allows you to pass typed objects directly:
70
+
71
+ ```python
72
+ from dataclasses import dataclass
73
+
74
+ @dataclass
75
+ class UserData:
76
+ name: str
77
+ age: int
78
+
79
+ async with client:
80
+ # Complex arguments are automatically serialized
81
+ result = await client.get_prompt("analyze_user", {
82
+ "user": UserData(name="Alice", age=30), # Automatically serialized to JSON
83
+ "preferences": {"theme": "dark"}, # Dict serialized to JSON string
84
+ "scores": [85, 92, 78], # List serialized to JSON string
85
+ "simple_name": "Bob" # Strings passed through unchanged
86
+ })
87
+ ```
88
+
89
+ The client handles serialization using `pydantic_core.to_json()` for consistent formatting. FastMCP servers can automatically deserialize these JSON strings back to the expected types.
90
+
91
+ ### Serialization Examples
92
+
93
+ ```python
94
+ async with client:
95
+ result = await client.get_prompt("data_analysis", {
96
+ # These will be automatically serialized to JSON strings:
97
+ "config": {
98
+ "format": "csv",
99
+ "include_headers": True,
100
+ "delimiter": ","
101
+ },
102
+ "filters": [
103
+ {"field": "age", "operator": ">", "value": 18},
104
+ {"field": "status", "operator": "==", "value": "active"}
105
+ ],
106
+ # This remains a string:
107
+ "report_title": "Monthly Analytics Report"
108
+ })
109
+ ```
110
+
111
+ ## Working with Prompt Results
112
+
113
+ The `get_prompt()` method returns a `GetPromptResult` object containing a list of messages:
114
+
115
+ ```python
116
+ async with client:
117
+ result = await client.get_prompt("conversation_starter", {"topic": "climate"})
118
+
119
+ # Access individual messages
120
+ for i, message in enumerate(result.messages):
121
+ print(f"Message {i + 1}:")
122
+ print(f" Role: {message.role}")
123
+ print(f" Content: {message.content.text if hasattr(message.content, 'text') else message.content}")
124
+ ```
125
+
126
+ ## Raw MCP Protocol Access
127
+
128
+ For access to the complete MCP protocol objects, use the `*_mcp` methods:
129
+
130
+ ```python
131
+ async with client:
132
+ # Raw MCP method returns full protocol object
133
+ prompts_result = await client.list_prompts_mcp()
134
+ # prompts_result -> mcp.types.ListPromptsResult
135
+
136
+ prompt_result = await client.get_prompt_mcp("example_prompt", {"arg": "value"})
137
+ # prompt_result -> mcp.types.GetPromptResult
138
+ ```
139
+
140
+ ## Multi-Server Clients
141
+
142
+ When using multi-server clients, prompts are accessible without prefixing (unlike tools):
143
+
144
+ ```python
145
+ async with client: # Multi-server client
146
+ # Prompts from any server are directly accessible
147
+ result1 = await client.get_prompt("weather_prompt", {"city": "London"})
148
+ result2 = await client.get_prompt("assistant_prompt", {"query": "help"})
149
+ ```
150
+
151
+ ## Common Prompt Patterns
152
+
153
+ ### System Messages
154
+
155
+ Many prompts generate system messages for LLM configuration:
156
+
157
+ ```python
158
+ async with client:
159
+ result = await client.get_prompt("system_configuration", {
160
+ "role": "helpful assistant",
161
+ "expertise": "python programming"
162
+ })
163
+
164
+ # Typically returns messages with role="system"
165
+ system_message = result.messages[0]
166
+ print(f"System prompt: {system_message.content}")
167
+ ```
168
+
169
+ ### Conversation Templates
170
+
171
+ Prompts can generate multi-turn conversation templates:
172
+
173
+ ```python
174
+ async with client:
175
+ result = await client.get_prompt("interview_template", {
176
+ "candidate_name": "Alice",
177
+ "position": "Senior Developer"
178
+ })
179
+
180
+ # Multiple messages for a conversation flow
181
+ for message in result.messages:
182
+ print(f"{message.role}: {message.content}")
183
+ ```
184
+
185
+ <Tip>
186
+ Prompt arguments and their expected types depend on the specific prompt implementation. Check the server's documentation or use `list_prompts()` to see available arguments for each prompt.
187
+ </Tip>
docs/clients/resources.mdx ADDED
@@ -0,0 +1,171 @@
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
+ ---
2
+ title: Resource Operations
3
+ sidebarTitle: Resources
4
+ description: Learn how to list and read static and templated resources from MCP servers.
5
+ icon: folder-open
6
+ ---
7
+
8
+ import { VersionBadge } from '/snippets/version-badge.mdx'
9
+
10
+ <VersionBadge version="2.0.0" />
11
+
12
+ Resources are data sources exposed by MCP servers. They can be static files or dynamic templates that generate content based on parameters.
13
+
14
+ ## Types of Resources
15
+
16
+ MCP servers expose two types of resources:
17
+
18
+ - **Static Resources**: Fixed content accessible via URI (e.g., configuration files, documentation)
19
+ - **Resource Templates**: Dynamic resources that accept parameters to generate content (e.g., API endpoints, database queries)
20
+
21
+ ## Listing Resources
22
+
23
+ ### Static Resources
24
+
25
+ Use `list_resources()` to retrieve all static resources available on the server:
26
+
27
+ ```python
28
+ async with client:
29
+ resources = await client.list_resources()
30
+ # resources -> list[mcp.types.Resource]
31
+
32
+ for resource in resources:
33
+ print(f"Resource URI: {resource.uri}")
34
+ print(f"Name: {resource.name}")
35
+ print(f"Description: {resource.description}")
36
+ print(f"MIME Type: {resource.mimeType}")
37
+ ```
38
+
39
+ ### Resource Templates
40
+
41
+ Use `list_resource_templates()` to retrieve available resource templates:
42
+
43
+ ```python
44
+ async with client:
45
+ templates = await client.list_resource_templates()
46
+ # templates -> list[mcp.types.ResourceTemplate]
47
+
48
+ for template in templates:
49
+ print(f"Template URI: {template.uriTemplate}")
50
+ print(f"Name: {template.name}")
51
+ print(f"Description: {template.description}")
52
+ ```
53
+
54
+ ## Reading Resources
55
+
56
+ ### Static Resources
57
+
58
+ Read a static resource using its URI:
59
+
60
+ ```python
61
+ async with client:
62
+ # Read a static resource
63
+ content = await client.read_resource("file:///path/to/README.md")
64
+ # content -> list[mcp.types.TextResourceContents | mcp.types.BlobResourceContents]
65
+
66
+ # Access text content
67
+ if hasattr(content[0], 'text'):
68
+ print(content[0].text)
69
+
70
+ # Access binary content
71
+ if hasattr(content[0], 'blob'):
72
+ print(f"Binary data: {len(content[0].blob)} bytes")
73
+ ```
74
+
75
+ ### Resource Templates
76
+
77
+ Read from a resource template by providing the URI with parameters:
78
+
79
+ ```python
80
+ async with client:
81
+ # Read a resource generated from a template
82
+ # For example, a template like "weather://{{city}}/current"
83
+ weather_content = await client.read_resource("weather://london/current")
84
+
85
+ # Access the generated content
86
+ print(weather_content[0].text) # Assuming text JSON response
87
+ ```
88
+
89
+ ## Content Types
90
+
91
+ Resources can return different content types:
92
+
93
+ ### Text Resources
94
+
95
+ ```python
96
+ async with client:
97
+ content = await client.read_resource("resource://config/settings.json")
98
+
99
+ for item in content:
100
+ if hasattr(item, 'text'):
101
+ print(f"Text content: {item.text}")
102
+ print(f"MIME type: {item.mimeType}")
103
+ ```
104
+
105
+ ### Binary Resources
106
+
107
+ ```python
108
+ async with client:
109
+ content = await client.read_resource("resource://images/logo.png")
110
+
111
+ for item in content:
112
+ if hasattr(item, 'blob'):
113
+ print(f"Binary content: {len(item.blob)} bytes")
114
+ print(f"MIME type: {item.mimeType}")
115
+
116
+ # Save to file
117
+ with open("downloaded_logo.png", "wb") as f:
118
+ f.write(item.blob)
119
+ ```
120
+
121
+ ## Working with Multi-Server Clients
122
+
123
+ When using multi-server clients, resource URIs are automatically prefixed with the server name:
124
+
125
+ ```python
126
+ async with client: # Multi-server client
127
+ # Access resources from different servers
128
+ weather_icons = await client.read_resource("weather://weather/icons/sunny")
129
+ templates = await client.read_resource("resource://assistant/templates/list")
130
+
131
+ print(f"Weather icon: {weather_icons[0].blob}")
132
+ print(f"Templates: {templates[0].text}")
133
+ ```
134
+
135
+ ## Raw MCP Protocol Access
136
+
137
+ For access to the complete MCP protocol objects, use the `*_mcp` methods:
138
+
139
+ ```python
140
+ async with client:
141
+ # Raw MCP methods return full protocol objects
142
+ resources_result = await client.list_resources_mcp()
143
+ # resources_result -> mcp.types.ListResourcesResult
144
+
145
+ templates_result = await client.list_resource_templates_mcp()
146
+ # templates_result -> mcp.types.ListResourceTemplatesResult
147
+
148
+ content_result = await client.read_resource_mcp("resource://example")
149
+ # content_result -> mcp.types.ReadResourceResult
150
+ ```
151
+
152
+ ## Common Resource URI Patterns
153
+
154
+ Different MCP servers may use various URI schemes:
155
+
156
+ ```python
157
+ # File system resources
158
+ "file:///path/to/file.txt"
159
+
160
+ # Custom protocol resources
161
+ "weather://london/current"
162
+ "database://users/123"
163
+
164
+ # Generic resource protocol
165
+ "resource://config/settings"
166
+ "resource://templates/email"
167
+ ```
168
+
169
+ <Tip>
170
+ Resource URIs and their formats depend on the specific MCP server implementation. Check the server's documentation for available resources and their URI patterns.
171
+ </Tip>
docs/clients/roots.mdx ADDED
@@ -0,0 +1,42 @@
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
+ ---
2
+ title: Client Roots
3
+ sidebarTitle: Roots
4
+ description: Learn how to provide local context to MCP servers.
5
+ icon: tree
6
+ ---
7
+
8
+ import { VersionBadge } from '/snippets/version-badge.mdx'
9
+
10
+ <VersionBadge version="2.0.0" />
11
+
12
+ Roots are a way for clients to inform servers about the resources they have access to. Servers can use this information to adjust behavior or provide more relevant responses.
13
+
14
+ ## Setting Static Roots
15
+
16
+ Provide a list of roots when creating the client:
17
+
18
+ <CodeGroup>
19
+ ```python Static Roots
20
+ from fastmcp import Client
21
+
22
+ client = Client(
23
+ "my_mcp_server.py",
24
+ roots=["/path/to/root1", "/path/to/root2"]
25
+ )
26
+ ```
27
+
28
+ ```python Dynamic Roots Callback
29
+ from fastmcp import Client
30
+ from fastmcp.client.roots import RequestContext
31
+
32
+ async def roots_callback(context: RequestContext) -> list[str]:
33
+ print(f"Server requested roots (Request ID: {context.request_id})")
34
+ return ["/path/to/root1", "/path/to/root2"]
35
+
36
+ client = Client(
37
+ "my_mcp_server.py",
38
+ roots=roots_callback
39
+ )
40
+ ```
41
+ </CodeGroup>
42
+
docs/clients/sampling.mdx ADDED
@@ -0,0 +1,94 @@
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
+ ---
2
+ title: LLM Sampling
3
+ sidebarTitle: Sampling
4
+ description: Learn how to handle server-initiated LLM sampling requests.
5
+ icon: brain
6
+ ---
7
+
8
+ import { VersionBadge } from '/snippets/version-badge.mdx'
9
+
10
+ <VersionBadge version="2.0.0" />
11
+
12
+ MCP servers can request LLM completions from clients. The client handles these requests through a sampling handler callback.
13
+
14
+ ## Setting Up Sampling Handling
15
+
16
+ Provide a `sampling_handler` function when creating the client:
17
+
18
+ ```python
19
+ from fastmcp import Client
20
+ from fastmcp.client.sampling import (
21
+ SamplingMessage,
22
+ SamplingParams,
23
+ RequestContext,
24
+ )
25
+
26
+ async def sampling_handler(
27
+ messages: list[SamplingMessage],
28
+ params: SamplingParams,
29
+ context: RequestContext
30
+ ) -> str:
31
+ # Your LLM integration logic here
32
+ # Extract text from messages and generate a response
33
+ return "Generated response based on the messages"
34
+
35
+ client = Client(
36
+ "my_mcp_server.py",
37
+ sampling_handler=sampling_handler,
38
+ )
39
+ ```
40
+
41
+ ## Handler Parameters
42
+
43
+ The sampling handler receives:
44
+
45
+ - **`messages`**: List of `SamplingMessage` objects representing the conversation
46
+ - **`params`**: `SamplingParams` object with generation parameters (systemPrompt, maxTokens, temperature, etc.)
47
+ - **`context`**: `RequestContext` object with request metadata
48
+
49
+ ## Basic Example
50
+
51
+ ```python
52
+ async def basic_sampling_handler(
53
+ messages: list[SamplingMessage],
54
+ params: SamplingParams,
55
+ context: RequestContext
56
+ ) -> str:
57
+ # Extract message content
58
+ conversation = []
59
+ for message in messages:
60
+ content = message.content.text if hasattr(message.content, 'text') else str(message.content)
61
+ conversation.append(f"{message.role}: {content}")
62
+
63
+ # Use the system prompt if provided
64
+ system_prompt = params.systemPrompt or "You are a helpful assistant."
65
+
66
+ # Here you would integrate with your preferred LLM service
67
+ # This is just a placeholder response
68
+ return f"Response based on conversation: {' | '.join(conversation)}"
69
+
70
+ client = Client(
71
+ "my_mcp_server.py",
72
+ sampling_handler=basic_sampling_handler
73
+ )
74
+ ```
75
+
76
+ ## Accessing Parameters
77
+
78
+ ```python
79
+ async def parameter_handler(
80
+ messages: list[SamplingMessage],
81
+ params: SamplingParams,
82
+ context: RequestContext
83
+ ) -> str:
84
+ # Available parameters from the server
85
+ system_prompt = params.systemPrompt
86
+ max_tokens = params.maxTokens
87
+ temperature = params.temperature
88
+ top_p = params.topP
89
+ stop_sequences = params.stopSequences
90
+
91
+ # Use these parameters with your LLM service
92
+ return "Generated response"
93
+ ```
94
+
docs/clients/tools.mdx ADDED
@@ -0,0 +1,143 @@
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
+ ---
2
+ title: Tool Operations
3
+ sidebarTitle: Tools
4
+ description: Learn how to discover and execute tools on MCP servers.
5
+ icon: wrench
6
+ ---
7
+
8
+ import { VersionBadge } from '/snippets/version-badge.mdx'
9
+
10
+ <VersionBadge version="2.0.0" />
11
+
12
+ Tools are executable functions exposed by MCP servers. The FastMCP client provides methods to discover available tools and execute them with arguments.
13
+
14
+ ## Discovering Tools
15
+
16
+ Use `list_tools()` to retrieve all tools available on the server:
17
+
18
+ ```python
19
+ async with client:
20
+ tools = await client.list_tools()
21
+ # tools -> list[mcp.types.Tool]
22
+
23
+ for tool in tools:
24
+ print(f"Tool: {tool.name}")
25
+ print(f"Description: {tool.description}")
26
+ if tool.inputSchema:
27
+ print(f"Parameters: {tool.inputSchema}")
28
+ ```
29
+
30
+ ## Executing Tools
31
+
32
+ ### Basic Execution
33
+
34
+ Execute a tool using `call_tool()` with the tool name and arguments:
35
+
36
+ ```python
37
+ async with client:
38
+ # Simple tool call
39
+ result = await client.call_tool("add", {"a": 5, "b": 3})
40
+ # result -> list[mcp.types.TextContent | mcp.types.ImageContent | ...]
41
+
42
+ # Access the result content
43
+ print(result[0].text) # Assuming TextContent, e.g., '8'
44
+ ```
45
+
46
+ ### Advanced Execution Options
47
+
48
+ The `call_tool()` method supports additional parameters for timeout control and progress monitoring:
49
+
50
+ ```python
51
+ async with client:
52
+ # With timeout (aborts if execution takes longer than 2 seconds)
53
+ result = await client.call_tool(
54
+ "long_running_task",
55
+ {"param": "value"},
56
+ timeout=2.0
57
+ )
58
+
59
+ # With progress handler (to track execution progress)
60
+ result = await client.call_tool(
61
+ "long_running_task",
62
+ {"param": "value"},
63
+ progress_handler=my_progress_handler
64
+ )
65
+ ```
66
+
67
+ **Parameters:**
68
+ - `name`: The tool name (string)
69
+ - `arguments`: Dictionary of arguments to pass to the tool (optional)
70
+ - `timeout`: Maximum execution time in seconds (optional, overrides client-level timeout)
71
+ - `progress_handler`: Progress callback function (optional, overrides client-level handler)
72
+
73
+ ## Handling Results
74
+
75
+ Tool execution returns a list of content objects. The most common types are:
76
+
77
+ - **`TextContent`**: Text-based results with a `.text` attribute
78
+ - **`ImageContent`**: Image data with image-specific attributes
79
+ - **`BlobContent`**: Binary data content
80
+
81
+ ```python
82
+ async with client:
83
+ result = await client.call_tool("get_weather", {"city": "London"})
84
+
85
+ for content in result:
86
+ if hasattr(content, 'text'):
87
+ print(f"Text result: {content.text}")
88
+ elif hasattr(content, 'data'):
89
+ print(f"Binary data: {len(content.data)} bytes")
90
+ ```
91
+
92
+ ## Error Handling
93
+
94
+ ### Exception-Based Error Handling
95
+
96
+ By default, `call_tool()` raises a `ToolError` if the tool execution fails:
97
+
98
+ ```python
99
+ from fastmcp.exceptions import ToolError
100
+
101
+ async with client:
102
+ try:
103
+ result = await client.call_tool("potentially_failing_tool", {"param": "value"})
104
+ print("Tool succeeded:", result)
105
+ except ToolError as e:
106
+ print(f"Tool failed: {e}")
107
+ ```
108
+
109
+ ### Manual Error Checking
110
+
111
+ For more granular control, use `call_tool_mcp()` which returns the raw MCP protocol object with an `isError` flag:
112
+
113
+ ```python
114
+ async with client:
115
+ result = await client.call_tool_mcp("potentially_failing_tool", {"param": "value"})
116
+ # result -> mcp.types.CallToolResult
117
+
118
+ if result.isError:
119
+ print(f"Tool failed: {result.content}")
120
+ else:
121
+ print(f"Tool succeeded: {result.content}")
122
+ ```
123
+
124
+ ## Argument Handling
125
+
126
+ Arguments are passed as a dictionary to the tool:
127
+
128
+ ```python
129
+ async with client:
130
+ # Simple arguments
131
+ result = await client.call_tool("greet", {"name": "World"})
132
+
133
+ # Complex arguments
134
+ result = await client.call_tool("process_data", {
135
+ "config": {"format": "json", "validate": True},
136
+ "items": [1, 2, 3, 4, 5],
137
+ "metadata": {"source": "api", "version": "1.0"}
138
+ })
139
+ ```
140
+
141
+ <Tip>
142
+ For multi-server clients, tool names are automatically prefixed with the server name (e.g., `weather_get_forecast` for a tool named `get_forecast` on the `weather` server).
143
+ </Tip>
docs/docs.json CHANGED
@@ -94,13 +94,31 @@
94
  "group": "Clients",
95
  "pages": [
96
  "clients/client",
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
97
  "clients/transports",
98
  {
99
  "group": "Authentication",
100
  "icon": "user-shield",
101
  "pages": ["clients/auth/oauth", "clients/auth/bearer"]
102
- },
103
- "clients/advanced-features"
104
  ]
105
  },
106
  {
 
94
  "group": "Clients",
95
  "pages": [
96
  "clients/client",
97
+ {
98
+ "group": "Core Interactions",
99
+ "icon": "handshake",
100
+ "pages": [
101
+ "clients/tools",
102
+ "clients/resources",
103
+ "clients/prompts"
104
+ ]
105
+ },
106
+ {
107
+ "group": "Advanced Features",
108
+ "icon": "stars",
109
+ "pages": [
110
+ "clients/logging",
111
+ "clients/progress",
112
+ "clients/sampling",
113
+ "clients/roots"
114
+ ]
115
+ },
116
  "clients/transports",
117
  {
118
  "group": "Authentication",
119
  "icon": "user-shield",
120
  "pages": ["clients/auth/oauth", "clients/auth/bearer"]
121
+ }
 
122
  ]
123
  },
124
  {
justfile CHANGED
@@ -24,4 +24,7 @@ api-ref *MODULES:
24
 
25
  # Clean up API reference documentation
26
  api-ref-clean:
27
- rm -rf docs/python-sdk
 
 
 
 
24
 
25
  # Clean up API reference documentation
26
  api-ref-clean:
27
+ rm -rf docs/python-sdk
28
+
29
+ copy-context:
30
+ uvx --with-editable . --refresh-package copychat copychat@latest src/ docs/ -x changelog.mdx -x python-sdk/ -v