mcp-bastion-fastmcp

Security middleware for FastMCP servers powered by MCP-Bastion.

Protect any FastMCP server from prompt injection, PII leakage, and resource exhaustion with a single import.

Install

pip install mcp-bastion-fastmcp

Usage

from mcp.server.fastmcp import FastMCP
from mcp_bastion_fastmcp import secure_fastmcp

mcp = FastMCP("My Secure Server")

# Add MCP-Bastion security to your server
secure_fastmcp(mcp)

@mcp.tool()
def get_weather(city: str) -> str:
    return f"Weather in {city}: 22C, sunny"

if __name__ == "__main__":
    mcp.run(transport="streamable-http")

What it protects

Scans all tool arguments through the same MCPBastionMiddleware path as the core Python package (see defaults on the three toggles above)
For full bastion.yaml features (semantic firewall, OPA/Cedar, allowlists, session limits, etc.), use build_middleware_from_config() with the low-level MCP Server - FastMCP does not expose a native hook for the entire policy surface

Implementation note: secure_fastmcp patches FastMCP._tool_manager.call_tool so every tool invocation flows through Bastion. Call it right after FastMCP(...) and before run().

License

Same terms as the MCP-Bastion project: see LICENSE. Non-commercial use is free with required citation/attribution; copyright terms apply. Commercial use as defined in the License may need a separate agreement (COMMERCIAL_LICENSE.md).

Development Status
- 4 - Beta
Intended Audience
- Developers
License
- Other/Proprietary License
Programming Language
- Python :: 3
Topic
- Security

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