How can I return different sets of tools depending on the client?

[HQidea]

For example, I want to return tools A and B for Claude and tools C and D for Openai.

Since version 2.13, I can access the client info during the initialization phase, but the context is not ready at that point. When the context becomes ready, the client info is no longer available.

Any guidance would be appreciated. Thanks!

[bytedev999]

I would be careful about making the tool list depend on ctx, because ctx exists for individual MCP operations, while tool discovery happens earlier through list_tools.

In practice, I’d solve this one of two ways.

The simplest option is to expose separate MCP endpoints/servers per client:

/mcp/claude   -> tools A, B
/mcp/openai   -> tools C, D

[scastria]

This is a builtin feature of fastmcp. You can use the AuthMiddleware and the check_auth callback which is called for every tool in list/tools. This check_auth callback is provided an AuthContext which contains the user's token. This allows you to inspect the token and compare its claims against the tool being checked and return True or False to show or hide it.