{"id":44926,"library":"fastmcp-slim","title":"FastMCP Slim","description":"FastMCP (slim variant) is a Python framework for building MCP (Model Context Protocol) servers quickly and with minimal dependencies. It provides a high-level abstraction over JSON-RPC and Streamable HTTP transports, allowing you to define tools, resources, and prompts with simple decorators. Version 3.4.2, active development.","status":"active","version":"3.4.2","language":"python","source_language":"en","source_url":"https://github.com/PrefectHQ/fastmcp","tags":["mcp","model-context-protocol","fastmcp","slim","json-rpc"],"install":[{"cmd":"pip install fastmcp-slim","lang":"bash","label":"Install from PyPI"}],"dependencies":[],"imports":[{"wrong":"from mcp.server.fastmcp import FastMCP","symbol":"FastMCP","correct":"from fastmcp import FastMCP"}],"quickstart":{"code":"from mcp.server.fastmcp import FastMCP\nimport os\n\nmcp = FastMCP(\"My App\")\nif os.environ.get('MCP_API_KEY'):\n    mcp.auth = os.environ['MCP_API_KEY']\n\n@mcp.tool()\ndef add(a: int, b: int) -> int:\n    return a + b\n\nif __name__ == \"__main__\":\n    mcp.run()","lang":"python","description":"Minimal FastMCP server with one tool."},"warnings":[{"fix":"Always import from 'mcp.server.fastmcp'.","message":"Import path: Use 'from mcp.server.fastmcp import FastMCP'. The package name 'fastmcp-slim' does not match the import path.","severity":"gotcha","affected_versions":"all"},{"fix":"Use async def for tool definitions and call await when invoking tools. Check migration guide.","message":"Version 3.x moved to asynchronous core. Sync tools are wrapped; async is preferred. Some decorators changed.","severity":"breaking","affected_versions":">=3.0.0"},{"fix":"Explicitly set transport when creating FastMCP instance if you need SSE.","message":"Transport defaults: FastMCP now defaults to 'streamable-http' (JSON-RPC over HTTP) instead of stdio. If you need SSE, set transport='sse'.","severity":"gotcha","affected_versions":">=3.0.0"}],"env_vars":null,"search_vec":"'3.4.2':49 'abstract':28 'activ':50 'allow':37 'build':11 'context':14,55 'decor':47 'defin':40 'depend':21 'develop':51 'fastmcp':1,3,57 'framework':9 'high':26 'high-level':25 'http':35 'json':31,60 'json-rpc':30,59 'level':27 'mcp':12,52 'minim':20 'model':13,54 'model-context-protocol':53 'prompt':44 'protocol':15,56 'provid':23 'python':8 'quick':17 'resourc':42 'rpc':32,61 'server':16 'simpl':46 'slim':2,4,58 'streamabl':34 'tool':41 'transport':36 'variant':5 'version':48","created_at":"2026-06-07T12:52:30.464957+00:00","updated_at":"2026-06-07T12:52:30.464957+00:00","problems":{"verify_error":"Traceback (most recent call last):\n  File \"/tmp/tmp6_mudctc/venv/lib/python3.12/site-packages/fastmcp/server/__init__.py\", line 6, in <module>\n    from .context import Context\n  File \"/tmp/tmp6_mudctc/venv/lib/python3.12/site-packages/fastmcp/server/context.py\", line 13, in <module>\n    import mcp.t"},"ecosystem":"pypi","meta_description":null,"install_score":null,"quickstart_score":null,"quickstart_tag":null,"pypi_latest":null,"cli_name":null,"cli_version":null,"type":"library","homepage":"https://github.com/PrefectHQ/fastmcp","github":"https://github.com/PrefectHQ/fastmcp","docs":null,"changelog":null,"pypi":null,"npm":null,"openapi_spec":null,"status_page":null,"smithery":null,"categories":["ai-ml"],"base_url":null,"auth_type":null,"provenance":{"verified_status":"import_fail","verified_at":"2026-07-03","last_verified":"2026-07-03","next_check":"2026-07-10","install_tag":null}}