Pin FastMCP to 2.12.3 - Version 2.14.x breaks MCP tools visibility

[groksrc]

Problem

Users report that MCP tools are not visible in Claude Desktop after FastMCP was upgraded to 2.14.x in production. The tools are registered correctly server-side but clients cannot see them.

Root Cause

Our dependency constraint fastmcp>=2.10.2 allowed production to upgrade to FastMCP 2.14.1 + MCP SDK 1.24.0, while our lockfile had 2.12.3 + 1.14.0.

FastMCP 2.14.0 includes breaking changes:

• Tool name validation at registration time (SEP-986)
• Removed deprecated APIs (BearerAuthProvider, Context.get_http_request(), dependencies parameter)
• Mount/import argument changes

Evidence

• Production shows 17 tools registered correctly
• MCP endpoint responds and handles tools/list requests
• But Claude Desktop users report tools not visible
• User confirmed pinning to 2.12.3 fixes the issue

User Report

Discord conversation confirming fix: https://discord.com/channels/1368009106061000777/1381294195553341531/1451703784165343426

Solution

Pin FastMCP to 2.12.3 until we can properly test and migrate to 2.14.x.

Version Comparison

Package	Lockfile (working)	Production (broken)
fastmcp	2.12.3	2.14.1
mcp	1.14.0	1.24.0

References

• FastMCP 2.14 Release Notes
• FastMCP Breaking Changes Policy

[claude]

Claude finished @groksrc's task in 1m 54s —— View job • claude/issue-463-20251220-0115 • Create PR ➔

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Issue analyzed and fix implemented ✓

Issue Triage:

• Type: Bug (MCP tools not visible in Claude Desktop)
• Priority: High (affects production users)
• Component: MCP
• Complexity: Simple (dependency pin)
• Label Applied: bug

Analysis:

This is a critical bug where FastMCP 2.14.x introduced breaking changes that prevent Claude Desktop from seeing MCP tools, despite them being registered correctly server-side. The issue has been confirmed by users, with pinning to 2.12.3 resolving the problem.

Changes Made:

• Read and understand current dependency configuration
• Perform issue triage and apply labels
• Pin FastMCP to version 2.12.3 in pyproject.toml
• Commit and push changes
• Provide PR creation link

Implementation:

Changed pyproject.toml line 32 from:

"fastmcp>=2.10.2",

to:

"fastmcp==2.12.3",

This pins FastMCP to the last known working version (2.12.3) until the team can properly test and migrate to 2.14.x with its breaking changes.

Next Steps:

The lockfile (uv.lock) will need to be updated by running uv sync locally. The CI/CD pipeline should handle this automatically when the PR is merged.

| Branch: claude/issue-463-20251220-0115