hedron-mcp

Deny-by-default MCP Streamable HTTP projection for Hedron.

Package maturity: Beta · Repository package version: 0.2.4 · pin >=0.2.4,<0.3 Flagship extra: hedron[mcp] · Import: hedron_mcp The source tree and applications installed from PyPI use the Hedron 1.0 release and should pin the flagship extra to hedron[mcp]>=1.0.0. Disabled and empty until resources and tools are explicitly registered. MCP never grants authority beyond the authenticated principal.

Production-grade for the declared Supported inventory (phase 0.32 / RFC-0065 / D-060). Mutating tools remain Experimental and require allow_mutations=True.

Install

pip install "hedron[mcp]>=1.0.0"
# or
pip install "hedron-mcp>=0.2.4,<0.3"

Installing without registrations remains a no-op empty server.

When to use

• Deny-by-default MCP tool/resource projection from a Hedron FastAPI app
• Explicit, principal-bounded agent tool surfaces with app-owned authz/tenant hooks

Prefer leaving enabled=False (default) until registrations are intentional.

Quick start

import os
from hedron import Hedron
from hedron_mcp import McpProjection, McpResource, McpTool, mount_mcp

app = Hedron(
    title="MCP demo",
    security="standard",
    session_secret=os.environ.get("HEDRON_SESSION_SECRET", "dev-only"),
)

# Prefer session / host auth. Do not trust client headers unless a reverse
# proxy overwrites them; the default resolver never reads x-hedron-principal.
projection = McpProjection(
    enabled=True,
    principal_resolver=lambda request: request.session.get("user"),
)
projection.register_resource(McpResource(uri="hedron://page/home", name="home"))
projection.register_tool(
    McpTool(
        name="status",
        schema={"type": "object", "properties": {}},
        mutate=False,
        handler=lambda: {"ok": True},
    )
)
mount_mcp(app, projection)  # Streamable HTTP at POST /mcp

See STABILITY, RELEASE_0_32, and upgrade fixtures.