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

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.

### Provider selection

Setting this environment variable allows the Scalekit provider to be used automatically without explicitly instantiating it in code.

<Card>
<ParamField path="FASTMCP_SERVER_AUTH" default="Not set">
Set to `fastmcp.server.auth.providers.scalekit.ScalekitProvider` to use Scalekit authentication.
</ParamField>
</Card>

### Scalekit-specific configuration

These environment variables provide default values for the Scalekit provider, whether it's instantiated manually or configured via `FASTMCP_SERVER_AUTH`.

<Card>
<ParamField path="FASTMCP_SERVER_AUTH_SCALEKITPROVIDER_ENVIRONMENT_URL" required>
Your Scalekit environment URL from the Admin Portal (e.g., `https://your-env.scalekit.com`)
</ParamField>

<ParamField path="FASTMCP_SERVER_AUTH_SCALEKITPROVIDER_RESOURCE_ID" required>
Your Scalekit resource server ID from the MCP Servers section
</ParamField>

<ParamField path="FASTMCP_SERVER_AUTH_SCALEKITPROVIDER_BASE_URL" required>
Public URL of your FastMCP server (e.g., `https://your-server.com` or `http://localhost:8000/` for development)
</ParamField>

Legacy `FASTMCP_SERVER_AUTH_SCALEKITPROVIDER_MCP_URL` is still recognized for backward compatibility but will be removed soon-rename it to `...BASE_URL`.

<ParamField path="FASTMCP_SERVER_AUTH_SCALEKITPROVIDER_REQUIRED_SCOPES" default="[]">
Comma-, space-, or JSON-separated list of scopes that tokens must include to access your server
</ParamField>
</Card>

Example `.env`:

```bash
# Use the Scalekit provider
FASTMCP_SERVER_AUTH=fastmcp.server.auth.providers.scalekit.ScalekitProvider

# Scalekit configuration
FASTMCP_SERVER_AUTH_SCALEKITPROVIDER_ENVIRONMENT_URL=https://your-env.scalekit.com
FASTMCP_SERVER_AUTH_SCALEKITPROVIDER_RESOURCE_ID=res_456
FASTMCP_SERVER_AUTH_SCALEKITPROVIDER_BASE_URL=https://your-server.com/
# FASTMCP_SERVER_AUTH_SCALEKITPROVIDER_REQUIRED_SCOPES=read,write
# FASTMCP_SERVER_AUTH_SCALEKITPROVIDER_MCP_URL=https://your-server.com/  # Deprecated
```

With environment variables set, your server code simplifies to:

```python server.py
from fastmcp import FastMCP

# Authentication is automatically configured from environment
mcp = FastMCP(name="My Scalekit Protected Server")

@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"}
```
