ceos/fastmcp
1
0
Fork 0
mirror of https://github.com/PrefectHQ/fastmcp.git synced 2026-08-26 23:44:17 +02:00
Code Issues Projects Releases Packages Wiki Activity

Fix middleware tests

Browse source
This commit is contained in:
Jeremiah Lowin 2025-06-26 18:13:32 -04:00
commit ddb38bacc4
5 changed files with 71 additions and 30 deletions
Download patch file Download diff file Expand all files Collapse all files

11
docs/servers/middleware.mdx
View file

@ -78,10 +78,13 @@ When a request comes in, **multiple hooks may be called for the same request**,
2. **`on_request` or `on_notification`** - Called based on the message type
3. **Operation-specific hooks** - Called for specific MCP operations like `on_call_tool`
For example, when a client calls a tool, your middleware will receive **three separate hook calls**:
1. First: `on_message` (because it's any MCP message)
2. Second: `on_request` (because tool calls expect responses)
3. Third: `on_call_tool` (because it's specifically a tool execution)
For example, when a client calls a tool, your middleware will receive **multiple hook calls**:
1. `on_message` and `on_request` for any initial tool discovery operations (list_tools)
2. `on_message` (because it's any MCP message) for the tool call itself
3. `on_request` (because tool calls expect responses) for the tool call itself
4. `on_call_tool` (because it's specifically a tool execution) for the tool call itself
Note that the MCP SDK may perform additional operations like listing tools for caching purposes, which will trigger additional middleware calls beyond just the direct tool execution.
This hierarchy allows you to target your middleware logic with the right level of specificity. Use `on_message` for broad concerns like logging, `on_request` for authentication, and `on_call_tool` for tool-specific logic like performance monitoring.