fastmcp/docs/python-sdk/fastmcp-server-middleware-middleware.mdx
2025-08-01 20:39:55 -04:00

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---
title: middleware
sidebarTitle: middleware
---
# `fastmcp.server.middleware.middleware`
## Functions
### `make_middleware_wrapper` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L66" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
make_middleware_wrapper(middleware: Middleware, call_next: CallNext[T, R]) -> CallNext[T, R]
```
Create a wrapper that applies a single middleware to a context. The
closure bakes in the middleware and call_next function, so it can be
passed to other functions that expect a call_next function.
## Classes
### `CallNext` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L42" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `MiddlewareContext` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L47" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Unified context for all middleware operations.
**Methods:**
#### `copy` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L62" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
copy(self, **kwargs: Any) -> MiddlewareContext[T]
```
### `Middleware` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L79" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Base class for FastMCP middleware with dispatching hooks.
**Methods:**
#### `on_message` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L126" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
on_message(self, context: MiddlewareContext[Any], call_next: CallNext[Any, Any]) -> Any
```
#### `on_request` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L133" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
on_request(self, context: MiddlewareContext[mt.Request], call_next: CallNext[mt.Request, Any]) -> Any
```
#### `on_notification` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L140" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
on_notification(self, context: MiddlewareContext[mt.Notification], call_next: CallNext[mt.Notification, Any]) -> Any
```
#### `on_call_tool` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L147" 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
```
#### `on_read_resource` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L154" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
on_read_resource(self, context: MiddlewareContext[mt.ReadResourceRequestParams], call_next: CallNext[mt.ReadResourceRequestParams, mt.ReadResourceResult]) -> mt.ReadResourceResult
```
#### `on_get_prompt` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L161" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
on_get_prompt(self, context: MiddlewareContext[mt.GetPromptRequestParams], call_next: CallNext[mt.GetPromptRequestParams, mt.GetPromptResult]) -> mt.GetPromptResult
```
#### `on_list_tools` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L168" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
on_list_tools(self, context: MiddlewareContext[mt.ListToolsRequest], call_next: CallNext[mt.ListToolsRequest, list[Tool]]) -> list[Tool]
```
#### `on_list_resources` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L175" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
on_list_resources(self, context: MiddlewareContext[mt.ListResourcesRequest], call_next: CallNext[mt.ListResourcesRequest, list[Resource]]) -> list[Resource]
```
#### `on_list_resource_templates` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L182" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
on_list_resource_templates(self, context: MiddlewareContext[mt.ListResourceTemplatesRequest], call_next: CallNext[mt.ListResourceTemplatesRequest, list[ResourceTemplate]]) -> list[ResourceTemplate]
```
#### `on_list_prompts` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/middleware.py#L189" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
on_list_prompts(self, context: MiddlewareContext[mt.ListPromptsRequest], call_next: CallNext[mt.ListPromptsRequest, list[Prompt]]) -> list[Prompt]
```