Fastmcp Django

FastMCP with Django

Use FastMCP to expose small, typed Django application capabilities to agents. Keep Django as the source of truth for auth, permissions, validation, models, transactions, and business rules. Treat FastMCP as the protocol layer around existing application services.

Tool Choice

• Prefer the standalone fastmcp package (from fastmcp import FastMCP) for new Python MCP work in Django.
• Use the official MCP Python SDK (from mcp.server.fastmcp import FastMCP) when the project has already standardized on it, needs lower-level protocol control, or a host explicitly requires SDK behavior.
• Consider django-mcp-server only when the project needs a Django-native package that works inside WSGI or declaratively exposes models/DRF APIs. Audit generated tool contracts and permissions before exposing private data.
• If the app already has a deliberate public OpenAPI surface, generated or proxied tools can help for a first pass. For production agents, prefer hand-curated tools with purpose-built names, schemas, permissions, and bounded outputs.

FastMCP docs track the project's main branch, so re-check current docs when relying on recently added features or version badges.

Resource Routing

Load only the files needed for the current task:

Implementation Workflow

1. Read existing Django entrypoints first: manage.py, settings, asgi.py, wsgi.py, URL routing, auth middleware, APIs, background jobs, and deployment files.
2. Choose the transport boundary:
   • Use stdio for local desktop/editor MCP servers that run beside the app.
   • Use a separate FastMCP HTTP sidecar when Django is WSGI-only or MCP should scale independently.
   • Mount FastMCP into the Django ASGI process when the app already runs under ASGI and sharing process/domain is intentional.
3. Put MCP server registration in a small module such as apps/core/mcp.py or project/mcp.py.
4. Keep tool bodies thin. Call existing services, selectors, forms, serializers, policy methods, or domain functions.
5. Add tests through fastmcp.Client before wiring the transport. Most behavior should be tested in memory without a running web server.

Core Rules

• Make every exposed capability explicit. Avoid generic SQL, generic model browsing, arbitrary imports, file path access, or "admin" tools unless the project has a clear allowlist and authorization plan.
• Use typed parameters, Pydantic constraints, return type annotations, docstrings, and small JSON-serializable return values.
• Pass durable identifiers, not Django model instances, request objects, lazy querysets, open files, or huge payloads.
• Paginate and cap list/search tools. Return stable IDs and summaries, not full model dumps.
• Inject the current user/account from validated auth context or a trusted dependency. Never let the model provide privileged identity fields in production.
• Use synchronous def FastMCP tools for ordinary Django ORM work unless the project has a clear async design.
• For long-lived MCP processes, call close_old_connections() around ORM work or centralize connection cleanup in a thin helper.
• Add timeouts to slow or externally dependent tools. Enqueue long-running work instead of holding MCP requests open.

Verification

• Inspect tool names, schemas, and descriptions with fastmcp list or fastmcp inspect when tool contracts matter.
• Test allowed and denied users for every permissioned tool.
• Test invalid inputs, missing objects, pagination caps, destructive action confirmation, database state changes, and transaction.on_commit side effects.
• Add one HTTP transport smoke test when ASGI mounting, auth headers, proxy behavior, or URL paths changed.

References

• FastMCP docs: https://gofastmcp.com/getting-started/welcome
• FastMCP GitHub: https://github.com/PrefectHQ/fastmcp
• FastMCP HTTP deployment: https://gofastmcp.com/deployment/http
• FastMCP tests: https://gofastmcp.com/development/tests
• FastMCP tools: https://gofastmcp.com/servers/tools
• FastMCP authentication: https://gofastmcp.com/servers/auth/authentication
• FastMCP dependency injection: https://gofastmcp.com/servers/dependency-injection
• Django async support: https://docs.djangoproject.com/en/5.2/topics/async/
• Django ASGI deployment: https://docs.djangoproject.com/en/5.2/howto/deployment/asgi/