How to control what MCP agents sends to tools ?

[pasilialx]

Hello.

I am new to MCP, so please bear with me — could you please tell me if it is possible to intervene in the call that MCPAgent makes to tools? I would like to review, fix, or change the tool input before it is sent. Preferably without forking the library or rewriting MCPAgent myself.

[arpieb]

It looks like at least in the FastMCP ecosystem, this is best accomplished on the MCP server side via middleware:

https://gofastmcp.com/servers/middleware

If you're implementing your own agent, then you should have full control over MCP tool calls. In that case, maybe wrap the tool call with your own function where you can perform that kind of bit-fiddling...?