---
title: response_limiting
sidebarTitle: response_limiting
---

# `fastmcp.server.middleware.response_limiting`


Response limiting middleware for controlling tool response sizes.

## Classes

### `ResponseLimitingMiddleware` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/response_limiting.py#L20" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Middleware that limits the response size of tool calls.

Intercepts tool call responses and enforces size limits. If a response
exceeds the limit, it extracts text content, truncates it, and returns
a single TextContent block.


**Methods:**

#### `on_call_tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/response_limiting.py#L93" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
on_call_tool(self, context: MiddlewareContext[mt.CallToolRequestParams], call_next: CallNext[mt.CallToolRequestParams, ToolResult]) -> ToolResult
```

Intercept tool calls and limit response size.

