How do I pass user info like (user_id, company_id, ...) from agent into MCP request Context?

[chungtran4078]

How do I pass user info like (user_id, company_id, ...) from agent into MCP request Context?
I would like to pass them through something like header, request context, not in parameter

[LokeshYarramallu]

did you get this sorted if yes please tell me how to

[twratl]

looking for the same!

[mukesh-shipthis]

headers = {
            "authorization": req_state.get().get("auth_token"),
        }
        async with streamablehttp_client(MCP_URL, headers) as (reader, writer, _):
            async with ClientSession(reader, writer) as session:
                await session.initialize()
                tools = await fetch_tools(session)

[AnudeepGadi]

@chungtran4078 If your MCP server will only be used by your own agents, then you can send custom headers to pass user_id, company_id. That works fine in a closed ecosystem where you control both client and server.

But if you want your MCP server to be usable by standard/public MCP clients (e.g. Claude Desktop or other open-source clients), headers aren’t a reliable option. The MCP spec doesn’t currently define a way for clients to send arbitrary headers or context, so those clients wouldn’t know what to send.

query_params may be an option. Ex: 127.0.0.1:8000/mcp?user_id=123
This is a workaround, as of now I don't see any standard MCP way of doing things for this problem.

I am also facing the same problem. Please let me know if you find a solution.

[streamnsight]

fastmcp/src/fastmcp/server/context.py

Line 158 in e66aa33

def request_context(self) -> RequestContext[ServerSession, Any, Request]:

The Context object gives you access to the underlying request context

[AnudeepGadi]

https://gofastmcp.com/python-sdk/fastmcp-server-dependencies

from fastmcp.server.dependencies you can import get_context, get_http_request and get_http_headers.

example:

from fastmcp.server.dependencies import get_http_headers

from fastmcp.server.middleware import Middleware, MiddlewareContext

class ToolCallMiddleware(Middleware):
    async def on_call_tool(self, context: MiddlewareContext, call_next):
        headers = get_http_headers()
        print(headers)
        result = await call_next(context) 
        return result

[suchith83]

If we are passing user_id in headers, then we need different client objects for different users right..!, is there any other way in which we can manage requests and responses for multiple user_id's with a single fastmcp/mcp client object? (without passing them to llm)

[twratl]

I do it with custom middleware

class ToolPolicyMiddleware(Middleware):
    async def on_call_tool(self, context: MiddlewareContext, call_next):
        tool_name = context.message.name

        frontend_request = context.fastmcp_context.get_http_request()
        original_headers = frontend_request.headers.mutablecopy()
        original_headers.update({"whatever": "you want"})
        frontend_request._headers = original_headers

        # Allow other tools to proceed
        return await call_next(context)

[pedro-inf-custodio]

I just tried this approach, but it doesn’t seem to work at the moment because the get_http_request method doesn’t exist on fastmcp_context. I’m also running into a similar issue when trying to override custom headers on a proxied MCP server.

I've tried a similar approach as well (using the code shared in this comment: #2819), but without success.