- Python 100%
65ea57963a* fix: filesystem provider import machinery - Temporary sys.path entries (both package and non-package mode) now removed immediately after exec_module via try/finally, eliminating permanent process-wide pollution - Non-package files use bare stem as sys.modules key only if unclaimed; falls back to private hash-based key to prevent stdlib shadowing (e.g. json.py clobbering json) - Reload of private-key modules uses spec.loader.exec_module directly instead of importlib.reload, which cannot find files by their private synthetic name - _find_package_root gains stop_at parameter; discover_and_import passes provider_root to prevent package root discovery from escaping above the provider boundary Closes #3625 (issues 2, 3, 6) 🤖 Generated with Claude Code * fix: use contextlib.suppress for SIM105 linting 🤖 Generated with Claude Code * test: add import machinery regression tests 🤖 Generated with Claude Code * fix: resolve provider_root before path comparison; improve tests - Resolve provider_root in import_module_from_file so the stop_at boundary in _find_package_root works correctly when provider_root is a relative path (e.g. FileSystemProvider(Path("./mcp"))) — previously the resolved file_path and unresolved stop_at.parent would never compare equal - Fix test_stdlib_not_shadowed: use unconditional finally to restore sys.modules["json"] - Strengthen test_same_stem_files: assert mod_a is not mod_b and that sys.modules["helpers"] was not clobbered by the second import - Replace direct _find_package_root unit test with an integration test through import_module_from_file(provider_root=...) that also verifies the module name and that tmp_path is not added to sys.path 🤖 Generated with Claude Code |
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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.