- Python 100%
68e76fea2e* fix: forward custom_route endpoints from mounted servers When a child server with custom HTTP routes (registered via @server.custom_route()) is mounted onto a parent, the routes were silently dropped because _get_additional_http_routes() only returned self._additional_http_routes without recursing into mounted providers. This caused 404s for endpoints like /readyz health checks that worked in v2 but broke in v3 (regression). The fix updates _get_additional_http_routes() to traverse providers, unwrap _WrappedProvider layers (from namespace transforms), find FastMCPProvider instances, and recursively collect their server's custom routes. Fixes #3457 * fix: narrow type annotation from BaseRoute to Route All items in _additional_http_routes are Route objects (created via Route(...) in custom_route()). Using list[Route] instead of list[BaseRoute] fixes the ty type checker failure where .path is accessed on BaseRoute which doesn't have that attribute. Removes unused BaseRoute imports from both server.py and transport.py. * fix: revert route type to list[BaseRoute] to fix ty errors The previous commit narrowed _additional_http_routes from list[BaseRoute] to list[Route], which broke: - component_manager appending Mount objects (Mount is BaseRoute, not Route) - tests assigning list[BaseRoute] variables (generics are invariant) Revert to list[BaseRoute] and use isinstance(r, Route) guards in tests for type-safe .path access. * fix: remove unused import and fix import grouping - Remove unused `Route` import from server.py - Fix import grouping in test_advanced.py (ruff check) * Address review: move imports to module root, type Provider, add collision note * fix: sort imports in transport.py --------- Co-authored-by: voidborne-d <voidborne-d@users.noreply.github.com> Co-authored-by: d 🔹 <258577966+voidborne-d@users.noreply.github.com> Co-authored-by: Jeremiah Lowin <153965+jlowin@users.noreply.github.com> |
||
|---|---|---|
| .claude | ||
| .cursor/rules | ||
| .github | ||
| docs | ||
| examples | ||
| scripts | ||
| skills/fastmcp-client-cli | ||
| src/fastmcp | ||
| tests | ||
| v3-notes | ||
| .ccignore | ||
| .coderabbit.yaml | ||
| .gitignore | ||
| .pre-commit-config.yaml | ||
| .python-version | ||
| AGENTS.md | ||
| CLAUDE.md | ||
| CODE_OF_CONDUCT.md | ||
| justfile | ||
| LICENSE | ||
| logo.py | ||
| loq.toml | ||
| pyproject.toml | ||
| README.md | ||
| SECURITY.md | ||
| uv.lock | ||
The Model Context Protocol (MCP) connects LLMs to tools and data. FastMCP gives you everything you need to go from prototype to production:
from fastmcp import FastMCP
mcp = FastMCP("Demo 🚀")
@mcp.tool
def add(a: int, b: int) -> int:
"""Add two numbers"""
return a + b
if __name__ == "__main__":
mcp.run()
Why FastMCP
Building an effective MCP application is harder than it looks. FastMCP handles all of it. Declare a tool with a Python function, and the schema, validation, and documentation are generated automatically. Connect to a server with a URL, and transport negotiation, authentication, and protocol lifecycle are managed for you. You focus on your logic, and the MCP part just works: with FastMCP, best practices are built in.
That's why FastMCP is the standard framework for working with MCP. FastMCP 1.0 was incorporated into the official MCP Python SDK in 2024. Today, the actively maintained standalone project is downloaded a million times a day, and some version of FastMCP powers 70% of MCP servers across all languages.
FastMCP has three pillars:
Servers Expose tools, resources, and prompts to LLMs. |
Apps Give your tools interactive UIs rendered directly in the conversation. |
Clients Connect to any MCP server — local or remote, programmatic or CLI. |
Servers wrap your Python functions into MCP-compliant tools, resources, and prompts. Clients connect to any server with full protocol support. And Apps give your tools interactive UIs rendered directly in the conversation.
Ready to build? Start with the installation guide or jump straight to the quickstart. When you're ready to deploy, Prefect Horizon offers free hosting for FastMCP users.
Installation
We recommend installing FastMCP with uv:
uv pip install fastmcp
For full installation instructions, including verification and upgrading, see the Installation Guide.
Upgrading? We have guides for:
📚 Documentation
FastMCP's complete documentation is available at gofastmcp.com, including detailed guides, API references, and advanced patterns.
Documentation is also available in llms.txt format, which is a simple markdown standard that LLMs can consume easily:
llms.txtis essentially a sitemap, listing all the pages in the documentation.llms-full.txtcontains the entire documentation. Note this may exceed the context window of your LLM.
Community: Join our Discord server to connect with other FastMCP developers and share what you're building.
Contributing
We welcome contributions! See the Contributing Guide for setup instructions, testing requirements, and PR guidelines.