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Basic Configuration

Add authentication parameters to your WidgetMCPServer: 
from fastapps import WidgetBuilder, WidgetMCPServer
from fastapps.cli.loader import auto_load_tools

# Build widgets
builder = WidgetBuilder(PROJECT_ROOT)
build_results = builder.build_all()
tools = auto_load_tools(build_results)

# Create server with authentication
server = WidgetMCPServer(
    name="my-widgets",
    widgets=tools,
    auth_issuer_url="https://tenant.auth0.com",
    auth_resource_server_url="https://example.com/mcp",
    auth_required_scopes=["user"],
)

app = server.get_app()

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With Audience

Some OAuth providers (like Auth0) require an audience claim: 
server = WidgetMCPServer(
    name="my-widgets",
    widgets=tools,
    auth_issuer_url="https://tenant.auth0.com",
    auth_resource_server_url="https://example.com/mcp",
    auth_audience="https://api.example.com",  # API identifier
    auth_required_scopes=["user"],
)

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Configuration Parameters

ParameterTypeRequiredDescription
auth_issuer_urlstrYes*OAuth issuer URL (e.g., https://tenant.auth0.com)
auth_resource_server_urlstrYes*Your MCP server URL (e.g., https://example.com/mcp)
auth_required_scopesList[str]NoRequired OAuth scopes (e.g., ["user", "read:data"])
auth_audiencestrNoJWT audience claim (required by some providers)
token_verifierTokenVerifierNoCustom token verifier (uses JWTVerifier by default)
* Both auth_issuer_url and auth_resource_server_url must be provided to enable authentication.

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Built-in JWT Verification

FastApps includes a JWTVerifier that automatically validates tokens.

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How It Works

The built-in verifier:
  1. Discovers JWKS URI from issuer’s .well-known/openid-configuration
  2. Validates JWT signature using public keys
  3. Verifies issuer, audience, expiration
  4. Checks required scopes
  5. Extracts user claims

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Example

server = WidgetMCPServer(
    name="my-widgets",
    widgets=tools,
    auth_issuer_url="https://tenant.auth0.com",
    auth_resource_server_url="https://example.com/mcp",
    auth_audience="https://api.example.com",
    auth_required_scopes=["user", "read:data"],
)
The server automatically:
  • Validates JWT signature
  • Verifies issuer matches https://tenant.auth0.com
  • Checks audience is https://api.example.com
  • Ensures token has user and read:data scopes

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Multiple Scopes

Require multiple scopes for all widgets: 
server = WidgetMCPServer(
    name="my-widgets",
    widgets=tools,
    auth_issuer_url="https://tenant.auth0.com",
    auth_resource_server_url="https://example.com/mcp",
    auth_required_scopes=["user", "read:data", "write:data"],
)
Users must have all specified scopes to access widgets.

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Complete Example

# server/main.py
import os
from pathlib import Path
from fastapps import WidgetBuilder, WidgetMCPServer
from fastapps.cli.loader import auto_load_tools

PROJECT_ROOT = Path(__file__).parent

# Build all widgets
builder = WidgetBuilder(PROJECT_ROOT)
build_results = builder.build_all()
tools = auto_load_tools(build_results)

# Create authenticated server
server = WidgetMCPServer(
    name="my-secure-widgets",
    widgets=tools,
    # OAuth Configuration
    auth_issuer_url=os.getenv("AUTH_ISSUER_URL"),
    auth_resource_server_url=os.getenv("AUTH_RESOURCE_SERVER_URL"),
    auth_audience=os.getenv("AUTH_AUDIENCE"),
    auth_required_scopes=["user"],
)

app = server.get_app()

if __name__ == "__main__":
    import uvicorn
    uvicorn.run(app, host="0.0.0.0", port=8001)

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Environment Variables

Store OAuth configuration in environment variables: 
# .env
AUTH_ISSUER_URL=https://your-tenant.us.auth0.com
AUTH_RESOURCE_SERVER_URL=https://yourdomain.com/mcp
AUTH_AUDIENCE=https://api.example.com
Load in your server: 
import os
from dotenv import load_dotenv

load_dotenv()

server = WidgetMCPServer(
    name="my-widgets",
    widgets=tools,
    auth_issuer_url=os.getenv("AUTH_ISSUER_URL"),
    auth_resource_server_url=os.getenv("AUTH_RESOURCE_SERVER_URL"),
    auth_audience=os.getenv("AUTH_AUDIENCE"),
    auth_required_scopes=["user"],
)

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Authentication Inheritance

Per MCP spec: “Missing field: inherit server default policy” When server authentication is enabled:
  • Widgets without decorators inherit server auth requirements
  • Widgets can opt-out with @no_auth
  • Widgets can add scopes with @auth_required(scopes=[...])
  • Widgets can make auth optional with @optional_auth
See Widget Decorators for details.

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Next Steps

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