Support importing custom_route endpoints when mounting servers (#1470)

Co-authored-by: Jeremiah Lowin <jlowin@users.noreply.github.com>
Co-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>

docs/python-sdk/fastmcp-server-server.mdx

@@ -26,7 +26,7 @@ Default lifespan context manager that does nothing.
 - An empty context object
 
 
-### `add_resource_prefix` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L2162" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+### `add_resource_prefix` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L2182" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 add_resource_prefix(uri: str, prefix: str, prefix_format: Literal['protocol', 'path'] | None = None) -> str
@@ -64,7 +64,7 @@ add_resource_prefix("resource:///absolute/path", "prefix")
 - `ValueError`: If the URI doesn't match the expected protocol\://path format
 
 
-### `remove_resource_prefix` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L2222" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+### `remove_resource_prefix` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L2242" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 remove_resource_prefix(uri: str, prefix: str, prefix_format: Literal['protocol', 'path'] | None = None) -> str
@@ -103,7 +103,7 @@ remove_resource_prefix("resource://prefix//absolute/path", "prefix")
 - `ValueError`: If the URI doesn't match the expected protocol\://path format
 
 
-### `has_resource_prefix` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L2289" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+### `has_resource_prefix` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L2309" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 has_resource_prefix(uri: str, prefix: str, prefix_format: Literal['protocol', 'path'] | None = None) -> bool
@@ -147,31 +147,31 @@ False
 
 **Methods:**
 
-#### `settings` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L288" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `settings` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L289" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 settings(self) -> Settings
 ```
 
-#### `name` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L299" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `name` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L300" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 name(self) -> str
 ```
 
-#### `instructions` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L303" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `instructions` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L304" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 instructions(self) -> str | None
 ```
 
-#### `version` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L307" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `version` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L308" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 version(self) -> str | None
 ```
 
-#### `run_async` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L310" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `run_async` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L311" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 run_async(self, transport: Transport | None = None, show_banner: bool = True, **transport_kwargs: Any) -> None
@@ -183,7 +183,7 @@ Run the FastMCP server asynchronously.
 - `transport`: Transport protocol to use ("stdio", "sse", or "streamable-http")
 
 
-#### `run` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L340" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `run` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L341" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 run(self, transport: Transport | None = None, show_banner: bool = True, **transport_kwargs: Any) -> None
@@ -195,13 +195,13 @@ Run the FastMCP server. Note this is a synchronous function.
 - `transport`: Transport protocol to use ("stdio", "sse", or "streamable-http")
 
 
-#### `add_middleware` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L382" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `add_middleware` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L383" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 add_middleware(self, middleware: Middleware) -> None
 ```
 
-#### `get_tools` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L385" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `get_tools` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L386" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 get_tools(self) -> dict[str, Tool]
@@ -210,13 +210,13 @@ get_tools(self) -> dict[str, Tool]
 Get all registered tools, indexed by registered key.
 
 
-#### `get_tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L389" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `get_tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L390" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 get_tool(self, key: str) -> Tool
 ```
 
-#### `get_resources` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L395" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `get_resources` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L396" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 get_resources(self) -> dict[str, Resource]
@@ -225,13 +225,13 @@ get_resources(self) -> dict[str, Resource]
 Get all registered resources, indexed by registered key.
 
 
-#### `get_resource` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L399" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `get_resource` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L400" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 get_resource(self, key: str) -> Resource
 ```
 
-#### `get_resource_templates` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L405" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `get_resource_templates` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L406" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 get_resource_templates(self) -> dict[str, ResourceTemplate]
@@ -240,7 +240,7 @@ get_resource_templates(self) -> dict[str, ResourceTemplate]
 Get all registered resource templates, indexed by registered key.
 
 
-#### `get_resource_template` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L409" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `get_resource_template` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L410" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 get_resource_template(self, key: str) -> ResourceTemplate
@@ -249,7 +249,7 @@ get_resource_template(self, key: str) -> ResourceTemplate
 Get a registered resource template by key.
 
 
-#### `get_prompts` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L416" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `get_prompts` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L417" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 get_prompts(self) -> dict[str, Prompt]
@@ -258,13 +258,13 @@ get_prompts(self) -> dict[str, Prompt]
 List all available prompts.
 
 
-#### `get_prompt` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L422" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `get_prompt` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L423" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 get_prompt(self, key: str) -> Prompt
 ```
 
-#### `custom_route` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L428" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `custom_route` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L429" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 custom_route(self, path: str, methods: list[str], name: str | None = None, include_in_schema: bool = True) -> Callable[[Callable[[Request], Awaitable[Response]]], Callable[[Request], Awaitable[Response]]]
@@ -285,7 +285,7 @@ Starlette's reverse URL lookup feature)
 - `include_in_schema`: Whether to include in OpenAPI schema, defaults to True
 
 
-#### `add_tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L808" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `add_tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L827" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 add_tool(self, tool: Tool) -> Tool
@@ -303,7 +303,7 @@ with the Context type annotation. See the @tool decorator for examples.
 - The tool instance that was added to the server.
 
 
-#### `remove_tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L833" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `remove_tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L852" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 remove_tool(self, name: str) -> None
@@ -318,7 +318,7 @@ Remove a tool from the server.
 - `NotFoundError`: If the tool is not found
 
 
-#### `add_tool_transformation` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L853" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `add_tool_transformation` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L872" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 add_tool_transformation(self, tool_name: str, transformation: ToolTransformConfig) -> None
@@ -327,7 +327,7 @@ add_tool_transformation(self, tool_name: str, transformation: ToolTransformConfi
 Add a tool transformation.
 
 
-#### `remove_tool_transformation` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L859" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `remove_tool_transformation` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L878" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 remove_tool_transformation(self, tool_name: str) -> None
@@ -336,19 +336,19 @@ remove_tool_transformation(self, tool_name: str) -> None
 Remove a tool transformation.
 
 
-#### `tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L864" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L883" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 tool(self, name_or_fn: AnyFunction) -> FunctionTool
 ```
 
-#### `tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L880" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L899" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 tool(self, name_or_fn: str | None = None) -> Callable[[AnyFunction], FunctionTool]
 ```
 
-#### `tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L895" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L914" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 tool(self, name_or_fn: str | AnyFunction | None = None) -> Callable[[AnyFunction], FunctionTool] | FunctionTool
@@ -404,7 +404,7 @@ server.tool(my_function, name="custom_name")
 ```
 
 
-#### `add_resource` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1026" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `add_resource` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1045" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 add_resource(self, resource: Resource) -> Resource
@@ -419,7 +419,7 @@ Add a resource to the server.
 - The resource instance that was added to the server.
 
 
-#### `add_template` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1048" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `add_template` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1067" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 add_template(self, template: ResourceTemplate) -> ResourceTemplate
@@ -434,7 +434,7 @@ Add a resource template to the server.
 - The template instance that was added to the server.
 
 
-#### `add_resource_fn` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1070" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `add_resource_fn` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1089" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 add_resource_fn(self, fn: AnyFunction, uri: str, name: str | None = None, description: str | None = None, mime_type: str | None = None, tags: set[str] | None = None) -> None
@@ -454,7 +454,7 @@ has parameters, it will be registered as a template resource.
 - `tags`: Optional set of tags for categorizing the resource
 
 
-#### `resource` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1108" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `resource` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1127" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 resource(self, uri: str) -> Callable[[AnyFunction], Resource | ResourceTemplate]
@@ -514,7 +514,7 @@ async def get_weather(city: str) -> str:
 ```
 
 
-#### `add_prompt` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1245" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `add_prompt` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1264" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 add_prompt(self, prompt: Prompt) -> Prompt
@@ -529,19 +529,19 @@ Add a prompt to the server.
 - The prompt instance that was added to the server.
 
 
-#### `prompt` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1268" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `prompt` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1287" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 prompt(self, name_or_fn: AnyFunction) -> FunctionPrompt
 ```
 
-#### `prompt` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1281" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `prompt` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1300" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 prompt(self, name_or_fn: str | None = None) -> Callable[[AnyFunction], FunctionPrompt]
 ```
 
-#### `prompt` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1293" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `prompt` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1312" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 prompt(self, name_or_fn: str | AnyFunction | None = None) -> Callable[[AnyFunction], FunctionPrompt] | FunctionPrompt
@@ -619,7 +619,7 @@ Decorator to register a prompt.
             ```
 
 
-#### `run_stdio_async` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1434" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `run_stdio_async` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1453" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 run_stdio_async(self, show_banner: bool = True) -> None
@@ -628,7 +628,7 @@ run_stdio_async(self, show_banner: bool = True) -> None
 Run the server using stdio transport.
 
 
-#### `run_http_async` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1454" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `run_http_async` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1473" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 run_http_async(self, show_banner: bool = True, transport: Literal['http', 'streamable-http', 'sse'] = 'http', host: str | None = None, port: int | None = None, log_level: str | None = None, path: str | None = None, uvicorn_config: dict[str, Any] | None = None, middleware: list[ASGIMiddleware] | None = None, stateless_http: bool | None = None) -> None
@@ -647,7 +647,7 @@ Run the server using HTTP transport.
 - `stateless_http`: Whether to use stateless HTTP (defaults to settings.stateless_http)
 
 
-#### `run_sse_async` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1528" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `run_sse_async` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1547" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 run_sse_async(self, host: str | None = None, port: int | None = None, log_level: str | None = None, path: str | None = None, uvicorn_config: dict[str, Any] | None = None) -> None
@@ -656,7 +656,7 @@ run_sse_async(self, host: str | None = None, port: int | None = None, log_level:
 Run the server using SSE transport.
 
 
-#### `sse_app` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1556" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `sse_app` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1575" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 sse_app(self, path: str | None = None, message_path: str | None = None, middleware: list[ASGIMiddleware] | None = None) -> StarletteWithLifespan
@@ -670,7 +670,7 @@ Create a Starlette app for the SSE server.
 - `middleware`: A list of middleware to apply to the app
 
 
-#### `streamable_http_app` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1587" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `streamable_http_app` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1606" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 streamable_http_app(self, path: str | None = None, middleware: list[ASGIMiddleware] | None = None) -> StarletteWithLifespan
@@ -683,7 +683,7 @@ Create a Starlette app for the StreamableHTTP server.
 - `middleware`: A list of middleware to apply to the app
 
 
-#### `http_app` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1608" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `http_app` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1627" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 http_app(self, path: str | None = None, middleware: list[ASGIMiddleware] | None = None, json_response: bool | None = None, stateless_http: bool | None = None, transport: Literal['http', 'streamable-http', 'sse'] = 'http') -> StarletteWithLifespan
@@ -700,13 +700,13 @@ Create a Starlette app using the specified HTTP transport.
 - A Starlette application configured with the specified transport
 
 
-#### `run_streamable_http_async` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1657" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `run_streamable_http_async` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1676" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 run_streamable_http_async(self, host: str | None = None, port: int | None = None, log_level: str | None = None, path: str | None = None, uvicorn_config: dict[str, Any] | None = None) -> None
 ```
 
-#### `mount` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1682" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `mount` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1701" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 mount(self, server: FastMCP[LifespanResultT], prefix: str | None = None, as_proxy: bool | None = None) -> None
@@ -760,7 +760,7 @@ automatically determined based on whether the server has a custom lifespan
 - `prompt_separator`: Deprecated. Separator character for prompt names.
 
 
-#### `import_server` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1803" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `import_server` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1823" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 import_server(self, server: FastMCP[LifespanResultT], prefix: str | None = None, tool_separator: str | None = None, resource_separator: str | None = None, prompt_separator: str | None = None) -> None
@@ -801,7 +801,7 @@ applied using the protocol\://prefix/path format
 - `prompt_separator`: Deprecated. Separator for prompt names.
 
 
-#### `from_openapi` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1930" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `from_openapi` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1950" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 from_openapi(cls, openapi_spec: dict[str, Any], client: httpx.AsyncClient, route_maps: list[RouteMap] | list[RouteMapNew] | None = None, route_map_fn: OpenAPIRouteMapFn | OpenAPIRouteMapFnNew | None = None, mcp_component_fn: OpenAPIComponentFn | OpenAPIComponentFnNew | None = None, mcp_names: dict[str, str] | None = None, tags: set[str] | None = None, **settings: Any) -> FastMCPOpenAPI | FastMCPOpenAPINew
@@ -810,7 +810,7 @@ from_openapi(cls, openapi_spec: dict[str, Any], client: httpx.AsyncClient, route
 Create a FastMCP server from an OpenAPI specification.
 
 
-#### `from_fastapi` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1979" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `from_fastapi` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L1999" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 from_fastapi(cls, app: Any, name: str | None = None, route_maps: list[RouteMap] | list[RouteMapNew] | None = None, route_map_fn: OpenAPIRouteMapFn | OpenAPIRouteMapFnNew | None = None, mcp_component_fn: OpenAPIComponentFn | OpenAPIComponentFnNew | None = None, mcp_names: dict[str, str] | None = None, httpx_client_kwargs: dict[str, Any] | None = None, tags: set[str] | None = None, **settings: Any) -> FastMCPOpenAPI | FastMCPOpenAPINew
@@ -819,7 +819,7 @@ from_fastapi(cls, app: Any, name: str | None = None, route_maps: list[RouteMap]
 Create a FastMCP server from a FastAPI application.
 
 
-#### `as_proxy` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L2042" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `as_proxy` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L2062" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 as_proxy(cls, backend: Client[ClientTransportT] | ClientTransport | FastMCP[Any] | AnyUrl | Path | MCPConfig | dict[str, Any] | str, **settings: Any) -> FastMCPProxy
@@ -833,7 +833,7 @@ instance or any value accepted as the `transport` argument of
 `fastmcp.client.Client` constructor.
 
 
-#### `from_client` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L2103" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+#### `from_client` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L2123" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
 
 ```python
 from_client(cls, client: Client[ClientTransportT], **settings: Any) -> FastMCPProxy
@@ -842,4 +842,4 @@ from_client(cls, client: Client[ClientTransportT], **settings: Any) -> FastMCPPr
 Create a FastMCP proxy server from a FastMCP client.
 
 
-### `MountedServer` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L2156" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
+### `MountedServer` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/server.py#L2176" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

docs/servers/composition.mdx

@@ -310,4 +310,8 @@ server = FastMCP("LegacyServer", resource_prefix_format="protocol")
 server = FastMCP("NewServer", resource_prefix_format="path")
 ```
 
-When mounting or importing servers, the prefix format of the parent server is used.
+When mounting or importing servers, the prefix format of the parent server is used.
+
+<Note>
+When mounting servers, custom HTTP routes defined with `@server.custom_route()` are also forwarded to the parent server, making them accessible through the parent's HTTP application.
+</Note>

src/fastmcp/server/http.py

@@ -229,7 +229,7 @@ def create_sse_app(
     # Add custom routes with lowest precedence
     if routes:
         server_routes.extend(routes)
-    server_routes.extend(server._additional_http_routes)
+    server_routes.extend(server._get_additional_http_routes())
 
     # Add middleware
     if middleware:
@@ -331,7 +331,7 @@ def create_streamable_http_app(
     # Add custom routes with lowest precedence
     if routes:
         server_routes.extend(routes)
-    server_routes.extend(server._additional_http_routes)
+    server_routes.extend(server._get_additional_http_routes())
 
     # Add middleware
     if middleware:

src/fastmcp/server/server.py

@@ -172,6 +172,7 @@ class FastMCP(Generic[LifespanResultT]):
         )
 
         self._additional_http_routes: list[BaseRoute] = []
+        self._mounted_servers: list[MountedServer] = []
         self._tool_manager = ToolManager(
             duplicate_behavior=on_duplicate_tools,
             mask_error_details=mask_error_details,
@@ -475,6 +476,24 @@ class FastMCP(Generic[LifespanResultT]):
 
         return decorator
 
+    def _get_additional_http_routes(self) -> list[BaseRoute]:
+        """Get all additional HTTP routes including from mounted servers.
+
+        Returns a list of all custom HTTP routes from this server and
+        recursively from all mounted servers.
+
+        Returns:
+            List of Starlette BaseRoute objects
+        """
+        routes = list(self._additional_http_routes)
+
+        # Recursively get routes from mounted servers
+        for mounted_server in self._mounted_servers:
+            mounted_routes = mounted_server.server._get_additional_http_routes()
+            routes.extend(mounted_routes)
+
+        return routes
+
     async def _mcp_list_tools(self) -> list[MCPTool]:
         logger.debug("Handler called: list_tools")
 
@@ -1796,6 +1815,7 @@ class FastMCP(Generic[LifespanResultT]):
             server=server,
             resource_prefix_format=self.resource_prefix_format,
         )
+        self._mounted_servers.append(mounted_server)
         self._tool_manager.mount(mounted_server)
         self._resource_manager.mount(mounted_server)
         self._prompt_manager.mount(mounted_server)

tests/server/test_mount.py

@@ -1019,3 +1019,125 @@ class TestResourceNamePrefixing:
         # The template name should also be prefixed
         template = templates["resource://prefix/user/{user_id}"]
         assert template.name == "prefix_user_template"
+
+
+class TestCustomRouteForwarding:
+    """Test that custom HTTP routes from mounted servers are forwarded."""
+
+    async def test_get_additional_http_routes_empty(self):
+        """Test _get_additional_http_routes returns empty list for server with no routes."""
+        server = FastMCP("TestServer")
+        routes = server._get_additional_http_routes()
+        assert routes == []
+
+    async def test_get_additional_http_routes_with_custom_route(self):
+        """Test _get_additional_http_routes returns server's own routes."""
+        server = FastMCP("TestServer")
+
+        @server.custom_route("/test", methods=["GET"])
+        async def test_route(request):
+            from starlette.responses import JSONResponse
+
+            return JSONResponse({"message": "test"})
+
+        routes = server._get_additional_http_routes()
+        assert len(routes) == 1
+        assert routes[0].path == "/test"  # type: ignore[attr-defined]
+
+    async def test_get_additional_http_routes_with_mounted_server(self):
+        """Test _get_additional_http_routes includes routes from mounted servers."""
+        main_server = FastMCP("MainServer")
+        sub_server = FastMCP("SubServer")
+
+        @sub_server.custom_route("/sub-route", methods=["GET"])
+        async def sub_route(request):
+            from starlette.responses import JSONResponse
+
+            return JSONResponse({"message": "from sub"})
+
+        # Mount the sub server
+        main_server.mount(sub_server, "sub")
+
+        routes = main_server._get_additional_http_routes()
+        assert len(routes) == 1
+        assert routes[0].path == "/sub-route"  # type: ignore[attr-defined]
+
+    async def test_get_additional_http_routes_recursive(self):
+        """Test _get_additional_http_routes works recursively with nested mounts."""
+        main_server = FastMCP("MainServer")
+        sub_server = FastMCP("SubServer")
+        nested_server = FastMCP("NestedServer")
+
+        @main_server.custom_route("/main-route", methods=["GET"])
+        async def main_route(request):
+            from starlette.responses import JSONResponse
+
+            return JSONResponse({"message": "from main"})
+
+        @sub_server.custom_route("/sub-route", methods=["GET"])
+        async def sub_route(request):
+            from starlette.responses import JSONResponse
+
+            return JSONResponse({"message": "from sub"})
+
+        @nested_server.custom_route("/nested-route", methods=["GET"])
+        async def nested_route(request):
+            from starlette.responses import JSONResponse
+
+            return JSONResponse({"message": "from nested"})
+
+        # Create nested mounting: main -> sub -> nested
+        sub_server.mount(nested_server, "nested")
+        main_server.mount(sub_server, "sub")
+
+        routes = main_server._get_additional_http_routes()
+
+        # Should include all routes
+        assert len(routes) == 3
+        route_paths = [route.path for route in routes]  # type: ignore[attr-defined]
+        assert "/main-route" in route_paths
+        assert "/sub-route" in route_paths
+        assert "/nested-route" in route_paths
+
+    async def test_mounted_servers_tracking(self):
+        """Test that _mounted_servers list tracks mounted servers correctly."""
+        main_server = FastMCP("MainServer")
+        sub_server1 = FastMCP("SubServer1")
+        sub_server2 = FastMCP("SubServer2")
+
+        # Initially no mounted servers
+        assert len(main_server._mounted_servers) == 0
+
+        # Mount first server
+        main_server.mount(sub_server1, "sub1")
+        assert len(main_server._mounted_servers) == 1
+        assert main_server._mounted_servers[0].server == sub_server1
+        assert main_server._mounted_servers[0].prefix == "sub1"
+
+        # Mount second server
+        main_server.mount(sub_server2, "sub2")
+        assert len(main_server._mounted_servers) == 2
+        assert main_server._mounted_servers[1].server == sub_server2
+        assert main_server._mounted_servers[1].prefix == "sub2"
+
+    async def test_multiple_routes_same_server(self):
+        """Test that multiple custom routes from same server are all included."""
+        server = FastMCP("TestServer")
+
+        @server.custom_route("/route1", methods=["GET"])
+        async def route1(request):
+            from starlette.responses import JSONResponse
+
+            return JSONResponse({"message": "route1"})
+
+        @server.custom_route("/route2", methods=["POST"])
+        async def route2(request):
+            from starlette.responses import JSONResponse
+
+            return JSONResponse({"message": "route2"})
+
+        routes = server._get_additional_http_routes()
+        assert len(routes) == 2
+        route_paths = [route.path for route in routes]  # type: ignore[attr-defined]
+        assert "/route1" in route_paths
+        assert "/route2" in route_paths