---
title: Scalekit 🤝 FastMCP
sidebarTitle: Scalekit
description: Secure your FastMCP server with Scalekit
icon: shield-check
---

import { VersionBadge } from "/snippets/version-badge.mdx"

<VersionBadge version="2.13.0" />

Install auth stack to your FastMCP server with [Scalekit](https://scalekit.com) using the [Remote OAuth](/servers/auth/remote-oauth) pattern: Scalekit handles user authentication, and the MCP server validates issued tokens.

### Prerequisites

Before you begin

1. Get a [Scalekit account](https://app.scalekit.com/) and grab your **Environment URL** from _Dashboard > Settings_ .
2. Have your FastMCP server's base URL ready (can be localhost for development, e.g., `http://localhost:8000/`)

### Step 1: Configure MCP server in Scalekit environment

<Steps>
<Step title="Register MCP server and set environment">

In your Scalekit dashboard:
    1. Open the **MCP Servers** section, then select **Create new server**
    2. Enter server details: a name, a resource identifier, and the desired MCP client authentication settings
    3. Save, then copy the **Resource ID** (for example, res_92015146095)

In your FastMCP project's `.env`:

```sh
SCALEKIT_ENVIRONMENT_URL=<YOUR_APP_ENVIRONMENT_URL>
SCALEKIT_RESOURCE_ID=<YOUR_APP_RESOURCE_ID> # res_926EXAMPLE5878
BASE_URL=http://localhost:8000/
# Optional: additional scopes tokens must have
# SCALEKIT_REQUIRED_SCOPES=read,write
```

</Step>
</Steps>

### Step 2: Add auth to FastMCP server

Create your FastMCP server file and use the ScalekitProvider to handle all the OAuth integration automatically:

> **Warning:** The legacy `mcp_url` and `client_id` parameters are deprecated and will be removed in a future release. Use `base_url` instead of `mcp_url` and remove `client_id` from your configuration.

```python server.py
from fastmcp import FastMCP
from fastmcp.server.auth.providers.scalekit import ScalekitProvider

# Discovers Scalekit endpoints and set up JWT token validation
auth_provider = ScalekitProvider(
    environment_url=SCALEKIT_ENVIRONMENT_URL,    # Scalekit environment URL
    resource_id=SCALEKIT_RESOURCE_ID,            # Resource server ID
    base_url=SERVER_URL,                         # Public MCP endpoint
    required_scopes=["read"],                    # Optional scope enforcement
)

# Create FastMCP server with auth
mcp = FastMCP(name="My Scalekit Protected Server", auth=auth_provider)

@mcp.tool
def auth_status() -> dict:
    """Show Scalekit authentication status."""
    # Extract user claims from the JWT
    return {
        "message": "This tool requires authentication via Scalekit",
        "authenticated": True,
        "provider": "Scalekit"
    }

```

<Tip>
Set `required_scopes` when you need tokens to carry specific permissions. Leave it unset to allow any token issued for the resource.
</Tip>

## Testing

### Start the MCP server

```sh
uv run python server.py
```

Use any MCP client (for example, mcp-inspector, Claude, VS Code, or Windsurf) to connect to the running serve. Verify that authentication succeeds and requests are authorized as expected.

## Production Configuration

For production deployments, load configuration from environment variables:

```python server.py
import os
from fastmcp import FastMCP
from fastmcp.server.auth.providers.scalekit import ScalekitProvider

# Load configuration from environment variables
auth = ScalekitProvider(
    environment_url=os.environ.get("SCALEKIT_ENVIRONMENT_URL"),
    resource_id=os.environ.get("SCALEKIT_RESOURCE_ID"),
    base_url=os.environ.get("BASE_URL", "https://your-server.com")
)

mcp = FastMCP(name="My Scalekit Protected Server", auth=auth)

@mcp.tool
def protected_action() -> str:
    """A tool that requires authentication."""
    return "Access granted via Scalekit!"
```

## Capabilities

Scalekit supports OAuth 2.1 with Dynamic Client Registration for MCP clients and enterprise SSO, and provides built‑in JWT validation and security controls.

**OAuth 2.1/DCR**: clients self‑register, use PKCE, and work with the Remote OAuth pattern without pre‑provisioned credentials.

**Validation and SSO**: tokens are verified (keys, RS256, issuer, audience, expiry), and SAML, OIDC, OAuth 2.0, ADFS, Azure AD, and Google Workspace are supported; use HTTPS in production and review auth logs as needed.

## Debugging

Enable detailed logging to troubleshoot authentication issues:

```python
import logging
logging.basicConfig(level=logging.DEBUG)
```

### Token inspection

You can inspect JWT tokens in your tools to understand the user context:

```python
from fastmcp.server.context import request_ctx
import jwt

@mcp.tool
def inspect_token() -> dict:
    """Inspect the current JWT token claims."""
    context = request_ctx.get()

    # Extract token from Authorization header
    if hasattr(context, 'request') and hasattr(context.request, 'headers'):
        auth_header = context.request.headers.get('authorization', '')
        if auth_header.startswith('Bearer '):
            token = auth_header[7:]
            # Decode without verification (already verified by provider)
            claims = jwt.decode(token, options={"verify_signature": False})
            return claims

    return {"error": "No token found"}
```
