FastAPI MCP MCP — Cas d'usage, Installer & Démo en direct

Pourquoi l'utiliser

Fonctionnalités clés

One-line mount: FastApiMCP(app).mount() — tools appear automatically
Schemas from Pydantic — no duplicate type definitions
FastAPI auth/deps still fire — middleware, Depends, OAuth2 just work
Filter which routes become tools via include/exclude tags

Démo en direct

Aperçu en pratique

fastapi-mcp.replay ▶ prêt

0/0

Installer

Choisissez votre client

~/Library/Application Support/Claude/claude_desktop_config.json · Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "fastapi-mcp": {
      "command": "uvx",
      "args": [
        "fastapi-mcp"
      ]
    }
  }
}

Ouvrez Claude Desktop → Settings → Developer → Edit Config. Redémarrez après avoir enregistré.

~/.cursor/mcp.json · .cursor/mcp.json

{
  "mcpServers": {
    "fastapi-mcp": {
      "command": "uvx",
      "args": [
        "fastapi-mcp"
      ]
    }
  }
}

Cursor utilise le même schéma mcpServers que Claude Desktop. La config projet l'emporte sur la globale.

VS Code → Cline → MCP Servers → Edit

{
  "mcpServers": {
    "fastapi-mcp": {
      "command": "uvx",
      "args": [
        "fastapi-mcp"
      ]
    }
  }
}

Cliquez sur l'icône MCP Servers dans la barre latérale Cline, puis "Edit Configuration".

~/.codeium/windsurf/mcp_config.json

{
  "mcpServers": {
    "fastapi-mcp": {
      "command": "uvx",
      "args": [
        "fastapi-mcp"
      ]
    }
  }
}

Même format que Claude Desktop. Redémarrez Windsurf pour appliquer.

~/.continue/config.json

{
  "mcpServers": [
    {
      "name": "fastapi-mcp",
      "command": "uvx",
      "args": [
        "fastapi-mcp"
      ]
    }
  ]
}

Continue utilise un tableau d'objets serveur plutôt qu'une map.

~/.config/zed/settings.json

{
  "context_servers": {
    "fastapi-mcp": {
      "command": {
        "path": "uvx",
        "args": [
          "fastapi-mcp"
        ]
      }
    }
  }
}

Ajoutez dans context_servers. Zed recharge à chaud à la sauvegarde.

claude mcp add fastapi-mcp -- uvx fastapi-mcp

Une seule ligne. Vérifiez avec claude mcp list. Supprimez avec claude mcp remove.

Cas d'usage

Usages concrets : FastAPI MCP

Expose an existing FastAPI app as MCP without refactoring

👤 Backend devs with a running FastAPI service ⏱ ~30 min intermediate

Quand l'utiliser : You already ship a FastAPI API. You want agents to use it. You don't want a parallel codebase.

Prérequis

Working FastAPI app with Pydantic models on requests/responses — If your routes return dict, refactor to Pydantic BaseModel first — otherwise tool schemas will be object

Déroulement

Install and mount

Add fastapi-mcp to my project. In my main.py, after app = FastAPI(), add FastApiMCP(app).mount(). Show the diff.✓ Copié

→ Minimal diff; server still runs
Verify tools appear

Run the server. Connect with npx -y mcp-remote http://localhost:8000/mcp. List tools — do all my GET/POST routes show up?✓ Copié

→ Tools listed, names match route operation_ids
Filter what's exposed

I don't want /admin/* routes exposed. Reconfigure with include_operations or exclude by tag.✓ Copié

→ Admin routes no longer in tool list

Résultat : Your existing API is now MCP-addressable with zero duplication of schemas or logic.

Pièges

Every route becomes a tool — including internal ones you didn't mean to expose — Explicitly set include_tags=['public'] or exclude_operations=[...] before going live
Routes without operation_id get generated names like read_item_items__item_id__get — ugly — Always set explicit operation_id on routes: @app.get('/items/{id}', operation_id='get_item')

Combiner avec : fastmcp

Expose an authenticated FastAPI app as MCP without breaking auth

👤 Backend devs with bearer/OAuth2 on FastAPI ⏱ ~30 min intermediate

Quand l'utiliser : Your FastAPI routes use Depends(get_current_user) — you need that to still fire when called via MCP.

Prérequis

Existing auth dependency — Depends(oauth2_scheme) or equivalent

Déroulement

Pass through the Authorization header

Configure fastapi-mcp to forward the Authorization header from MCP context to the underlying route. Point me at the settings.✓ Copié

→ Config change; routes now receive the header
Test an authed call

Call the protected endpoint via MCP. First with no token (expect 401), then with a valid one (expect 200).✓ Copié

→ 401 unauth, 200 auth — same as direct HTTP
Document the client-side setup

Write the mcp-remote config users need so their Claude Desktop passes an Authorization header.✓ Copié

→ Copy-pasteable client config snippet

Résultat : Auth enforced identically whether called from curl or from an agent.

Pièges

Agent accidentally uses a long-lived root token — Mint short-lived scoped tokens per user; rotate aggressively — treat MCP like any other API client

Deploy the MCP endpoint alongside your existing API

👤 Platform engineers ⏱ ~45 min advanced

Quand l'utiliser : You run FastAPI on Cloud Run / Fly / Render. You want MCP to share that deploy.

Déroulement

Mount at a stable path

Mount fastapi-mcp at /mcp. Confirm /docs (Swagger) and /mcp both work from the same process.✓ Copié

→ Both paths respond
Expose via your existing ingress

Update my Cloud Run / nginx / API gateway config to route /mcp to this service with SSE-compatible timeouts (no buffering, long idle).✓ Copié

→ Remote mcp-remote connects cleanly
Document the client setup

Write the team-facing README: how to add this MCP to Claude Desktop + Cursor.✓ Copié

→ Copy-paste config per client

Résultat : One deploy, two protocols (REST + MCP), zero extra infra.

Pièges

Proxy buffers SSE responses, connection appears hung — Disable proxy buffering — nginx: proxy_buffering off; Cloud Run: already fine; Cloudflare: enable streaming

Combiner avec : cloud-run · vercel

Combinaisons

Associez-le à d'autres MCPs pour un effet X10

fastapi-mcp + fastmcp

Use fastapi-mcp for legacy routes, FastMCP for greenfield agent-specific tools in the same process

Mount fastapi-mcp for my existing /api/* routes and register 3 new FastMCP tools for agent-only operations like bulk_sync.✓ Copié

fastapi-mcp + cloud-run

Deploy REST + MCP together on Cloud Run

Take my FastAPI service, add fastapi-mcp, containerize, and deploy to Cloud Run with IAM auth on /mcp.✓ Copié

Outils

Ce que ce MCP expose

Outil	Entrées	Quand appeler	Coût
FastApiMCP(app, **options)	app: FastAPI, include_operations?, exclude_operations?, include_tags?, exclude_tags?, name?, description?	Build-time wiring — create once at startup	free
.mount(path='/mcp')	path?	Right after instantiation	free
Auto-generated tools	derived from each FastAPI route's request/response models	No action — they appear once you mount	same as your route

Coût et limites

Coût d'exécution

Quota d'API: Inherits from your API
Tokens par appel: Same as direct HTTP calls — no overhead
Monétaire: Free, open source
Astuce: Exclude verbose admin/debug routes from MCP — they pollute the agent's tool list and cost tokens on every list_tools

Sécurité

Permissions, secrets, portée

Stockage des identifiants : Whatever your FastAPI uses — fastapi-mcp doesn't add a new auth layer

Sortie de données : Wherever your routes already go

Not first-party Anthropic — tadata-org community project. Pin to a specific version and review changes before bumping.

Dépannage

Erreurs courantes et correctifs

Tools appear but calls return 422 validation errors

Your route uses dict instead of Pydantic BaseModel — MCP passes typed JSON and your route can't parse it. Refactor to BaseModel.

Route exists at /items but no matching tool

fastapi-mcp skips routes without a response_model or operation_id in some cases. Add response_model=ItemOut and operation_id='get_item'.

Vérifier : curl http://localhost:8000/openapi.json | jq '.paths'

Auth dependency doesn't fire when called via MCP

Configure header forwarding in FastApiMCP options. If your dependency reads cookies instead of headers, switch to header-based auth — MCP has no cookie jar.

SSE hangs behind nginx

Add proxy_buffering off; proxy_cache off; proxy_read_timeout 3600s; to the /mcp location block.

Alternatives

FastAPI MCP vs autres

Alternative	Quand l'utiliser	Compromis
FastMCP	Greenfield — no existing FastAPI app, just writing an MCP server	Cleaner DX for new projects; fastapi-mcp wins for retrofitting
Hand-written SDK server	You need fine-grained control over tool names, descriptions, and schemas	More code, more maintenance — usually not worth it

Plus

Ressources

📖 Lire le README officiel sur GitHub

🐙 Voir les issues ouvertes

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