mcp-core

Auth, billing, and logging infrastructure for MCP-first servers. Sits between your product code and fastapi-mcp, with provider-aware auth for Logto and Supabase.

Your MCP Server  (product-specific tool handlers)
     mcp-core    (auth, billing, logging, health)
    fastapi-mcp  (MCP protocol: JSON-RPC, SSE, tool discovery)
      FastAPI

Install

pip install mcp-core-auth

The package is published as mcp-core-auth on PyPI (the bare mcp-core name is held by an unrelated project), but the import path is unchanged:

from mcp_core import MCPCore

Quick Start

from contextlib import asynccontextmanager
from fastapi import FastAPI, Request
from mcp_core import MCPCore

core = MCPCore(
    product_name="my-product",
    auth_provider="logto",
    logto_endpoint="https://your-tenant.logto.app",
    logto_api_resource="https://api.my-product.app",
    mongodb_uri="mongodb+srv://...",
    stripe_secret_key="sk_test_...",
    stripe_price_id="price_...",
    free_credits=30,
    tool_costs={"browse": 0, "generate": 5},
    read_only_tools={"browse"},
)

@asynccontextmanager
async def lifespan(app: FastAPI):
    await core.connect_db()
    yield

app = FastAPI(lifespan=lifespan)
core.install_routes(app)  # /health, /api/billing/credits, webhook, OAuth metadata

@app.post("/api/mcp/generate")
async def generate(request: Request):
    user = await core.auth_and_bill(request, "generate")
    result = do_generation()
    await core.log_tool_call(request, "generate", user=user, duration_ms=1200)
    return result

All config can also come from MCP_CORE_* environment variables.

To use Supabase Auth instead, switch the provider and pass your Supabase URL and anon key:

core = MCPCore(
    product_name="my-product",
    auth_provider="supabase",
    supabase_url="https://your-project.supabase.co",
    supabase_anon_key="sb_publishable_...",
    supabase_api_resource="https://api.my-product.app",
    mongodb_uri="mongodb+srv://...",
    free_credits=30,
    tool_costs={"browse": 0, "generate": 5},
    read_only_tools={"browse"},
)

If auth_provider is omitted, mcp-core infers Supabase when both MCP_CORE_SUPABASE_URL and MCP_CORE_SUPABASE_ANON_KEY are present; otherwise it preserves the existing Logto default.

Modules

Auth (mcp_core.auth)

Provider-aware bearer-token auth. Creates MongoDB user records on first auth using a neutral auth_user_id while preserving legacy logto_user_id fields for existing Logto apps.

• Logto JWT validation via JWKS
• Supabase access-token validation through Supabase Auth
• Cloud or self-hosted provider URLs
• 30s clock skew tolerance
• Race-condition-safe user upsert
• Dev bypass (Bearer dev-bypass) for local development
• M2M token rejection for paid tools

Billing (mcp_core.billing.StripeBilling)

Stripe billing for credit-based products and all-access subscription products.

• Credit mode deducts free credits first, then falls back to Stripe metered billing.
• Subscription mode (BILLING_MODE=subscription) requires an active subscription for paid tools and never consumes credits.
• Standard billing routes include /api/billing/credits, /api/billing/checkout-subscription, /api/billing/sync, /api/billing/portal, and /api/stripe/webhook.
• Subscription webhooks track checkout.session.completed, customer.subscription.created, customer.subscription.updated, customer.subscription.paused, customer.subscription.resumed, customer.subscription.deleted, invoice.payment_failed, invoice.payment_action_required, and invoice.paid.
• Access defaults to active, trialing, and past_due; unpaid, paused, incomplete, incomplete_expired, and canceled do not grant subscription access.
• Stripe Customer Portal should handle payment methods, invoices, receipts, and cancellation self-service. Stripe Billing customer-email settings should handle invoice, receipt, failed-payment, and renewal emails; auth providers such as Supabase should remain responsible for auth and security emails.

Useful subscription env vars:

BILLING_MODE=subscription
STRIPE_SECRET_KEY=sk_live_or_test_...
STRIPE_PRICE_ID=price_...
STRIPE_WEBHOOK_SECRET=whsec_...
STRIPE_PORTAL_CONFIGURATION_ID=bpc_...
SUBSCRIPTION_PLAN_NAME="Pro"
SUBSCRIPTION_PRICE_LABEL="$20/month"

Store billing and plans (mcp_core.store)

App Store subscriptions through RevenueCat, next to Stripe:

• PlanCatalog / Plan: map Stripe prices and store entitlements to plans. require_plan(core, user, "pro") reads both, and the highest plan wins.
• RevenueCatBilling: webhook (constant-time Authorization check, idempotent event log), reconcile(user) through the v1 REST API behind RevenueCatClient, a sandbox allowlist, and an on_change hook for product-owned allowances.
• core.install_store_routes(app) and core.install_account_routes(app, before_delete=...) (POST /api/account/delete).

See integration guide section 10.

Tool Logging (mcp_core.tool_logging.ToolLogger)

Audit trail for every MCP tool call. Writes to MongoDB tool_logs collection.

Health (mcp_core.health.HealthCheck)

Composable health check builder. Supports sync and async checks with timeouts.

Readiness (mcp_core.readiness)

Provider-aware MCP OAuth onboarding diagnostics. The bundled CLI follows the same discovery path as RFC 9728 clients:

mcp-core-check-readiness https://your-app.example.com/mcp/v2/

It checks protected-resource metadata, authorization-server discovery, Dynamic Client Registration, unauthenticated MCP bearer challenges, and provider-specific behavior for Logto and Supabase. For Supabase, it also verifies that the authorize endpoint redirects back to your app's consent UI with an authorization_id.

Client auth matrix (operators / products)

Server readiness is not enough for release confidence. Use the client auth matrix to verify real MCP clients (Claude Code, OpenCode, Grok, Cursor, …):

• docs/client-auth-matrix.md — OAuth primary vs optional PAT fallback; operator checklist; anti-patterns
• docs/templates/connect.md.template — plain-text connect guide products can serve at /.well-known/mcp/connect.md

Product-specific eval harnesses (isolated CLI profiles, Windows runners, etc.) belong in the product repo, not in mcp-core.

Testing

# Mock tests (no external services)
pip install -e ".[dev]"
pytest tests/ -v

# Live tests (requires .env.live with real credentials)
RUN_LIVE_TESTS=1 pytest tests/live/ -v

Contributing

Bug reports and PRs welcome. See CONTRIBUTING.md for the workflow and SECURITY.md for vulnerability reporting.

The multi-provider auth design reference lives in docs/multi-provider-auth-plan.md.

License

MIT