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

---
title: error_handling
sidebarTitle: error_handling
---

# `fastmcp.server.middleware.error_handling`


Error handling middleware for consistent error responses and tracking.

## Classes

### `ErrorHandlingMiddleware` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/error_handling.py#L15" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Middleware that provides consistent error handling and logging.

Catches exceptions, logs them appropriately, and converts them to
proper MCP error responses. Also tracks error patterns for monitoring.


**Methods:**

#### `on_message` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/error_handling.py#L110" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
on_message(self, context: MiddlewareContext, call_next: CallNext) -> Any
```

Handle errors for all messages.


#### `get_error_stats` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/error_handling.py#L121" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
get_error_stats(self) -> dict[str, int]
```

Get error statistics for monitoring.


### `RetryMiddleware` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/error_handling.py#L126" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Middleware that implements automatic retry logic for failed requests.

Retries requests that fail with transient errors, using exponential
backoff to avoid overwhelming the server or external dependencies.


**Methods:**

#### `on_request` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/error_handling.py#L182" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
on_request(self, context: MiddlewareContext, call_next: CallNext) -> Any
```

Implement retry logic for requests.