- Python 100%
e35a74f004* Add FastMCPApp — a Provider for composable MCP applications * Wire Prefab callable resolver via to_json(tool_resolver=) parameter * Remove inspect.signature compat check, use try/except until prefab 0.10.0 * Address review: fix add_tool registry gaps, normalize auth errors, bump prefab to 0.10.0 * Register global key after _add_component succeeds * Simplify: extract decorator dispatch, use get_fastmcp_meta, expose get_global_tool * Remove prek from Marvin workflows These workflows run Claude to respond to /marvin mentions — linting the repo is unnecessary and fails without renderer deps installed. * Return ResolvedTool from callable resolver, add contacts example The callable resolver now returns ResolvedTool (from prefab_ui) instead of a plain string, carrying metadata like unwrap_result that the renderer needs to correctly handle structuredContent envelopes. The unwrap_result flag is derived from the tool's x-fastmcp-wrap-result output schema marker. * Bump prefab-ui requirement to >=0.11.0 * Remove stale ty ignore comments now that prefab-ui 0.11 is published * Add fastmcp dev apps command with browser UI preview * Improve fastmcp dev apps: dropdown picker, reload flag, process cleanup - Replace Tabs with Pages+Select for tool picker (Rx-based reactive state) - Add --reload/--no-reload flag (default: True) to fastmcp dev apps - Kill entire process group on shutdown so port 8000 is freed properly - Suppress uvicorn websockets deprecation warning (websockets-sansio) - Bump prefab-ui to >=0.11.1 (fixes get_renderer_head bug in 0.11.0) - Add farewell tool to greet_server example for multi-tool testing * Add docs for fastmcp dev apps command * Fix orphaned server on startup failure, guard Unix-only signal handling * Show tool title in picker, remove editable prefab source * Bump prefab-ui to >=0.11.2 * Fail fast when prefab-ui is not installed * Add apps/development docs, link from prefab and sidebar * Fix optional field defaults, fail with non-zero on startup timeout |
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| .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.