fastmcp-extensions is an unofficial extension library for FastMCP, providing patterns, practices, and utilities to enhance FastMCP server development. It currently supports FastMCP v3 and includes features like dynamic tool filtering and a helper for MCP server credential resolution. The library is actively maintained by AirbyteHQ and undergoes periodic releases.
Install & Compatibility
Where this runs
tested against v0.5.0 · pip install
no network on importno background threads
Install × environment matrix
Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux
py 3.9
✕ build_error
✕ build_error
115MB installed
● package 115MB
Code
Verified usage
Verified import paths — ran on the pinned version, not inferred.
Based on release notes; specific modules for other extensions like dynamic tool filtering may vary.
from fastmcp_extensions.server import mcp_server
The core FastMCP object, which fastmcp-extensions extends.
from fastmcp import FastMCP
This quickstart demonstrates how to initialize a FastMCP server and conceptually integrate features provided by `fastmcp-extensions`, such as the `mcp_server` helper for server setup and credential resolution, and a placeholder for dynamic tool filtering. Due to the lack of specific examples in public documentation, some imports and usages are illustrative based on the library's stated features. Users should consult the library's source for precise API details.
import os
from fastmcp import FastMCP
# Assuming mcp_server helper is directly exposed in a 'server' module
# Exact import path for specific extensions may vary based on internal structure.
try:
from fastmcp_extensions.server import mcp_server
from fastmcp_extensions.filters import dynamic_filter_policy # Hypothetical import
except ImportError:
print("Warning: fastmcp-extensions specific imports not found. Using FastMCP core only.")
mcp_server = None # Placeholder
dynamic_filter_policy = None # Placeholder
def run_extended_mcp_server():
mcp = FastMCP(name="MyExtendedMCPServer")
@mcp.tool
def hello(name: str = "World") -> str:
"""Greets the given name."""
return f"Hello, {name}! This is an extended FastMCP server."
# Example of integrating an extension, if 'mcp_server' exists
if mcp_server:
# The mcp_server helper likely takes a FastMCP instance and applies configurations.
# This is a hypothetical usage based on 'built-in server info and credential resolution'.
print("Applying fastmcp-extensions mcp_server helper...")
# mcp_server might take parameters for credential resolution, e.g., via env vars.
# For example, os.environ.get('MCP_SERVER_SECRET_KEY', 'default_key')
configured_mcp = mcp_server(mcp, credentials_env_var='FASTMCP_API_KEY')
else:
configured_mcp = mcp
# If dynamic_filter_policy exists, it would likely be applied to the server
if dynamic_filter_policy:
print("Applying dynamic tool filtering policy...")
# configured_mcp.add_filter(dynamic_filter_policy())
print(f"Running {configured_mcp.name} with stdio transport...")
# In a real scenario, you'd run the server (e.g., in a __main__ block)
# configured_mcp.run(transport="stdio")
print("Server setup complete (not actually running in this snippet).")
print("Available tools on the server:")
for tool_name, tool_obj in configured_mcp._tools.items():
print(f"- {tool_name}: {tool_obj.description}")
if __name__ == "__main__":
# Set a dummy environment variable if needed for hypothetical credential resolution
os.environ['FASTMCP_API_KEY'] = 'fake_api_key_123'
run_extended_mcp_server()
Upgrade
Version history
Breaking-change detection hasn't run for this library yet.
Audit
Security & dependencies
CVE tracking and dependency tree are planned for a later release.