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ARIA MCP Gateway — Client+Server Authorization Proxy

What it is​

The ARIA MCP Gateway is a dual‑role MCP Client and MCP Server that sits in front of all MCP traffic. It connects to upstream MCP Servers (e.g., CRUDService Loopback MCP and vendor MCPs) as a client, and republishes a governed MCP endpoint as a server so agents and UIs talk to a single, secured entry point. It is part of the ARIA Shield product family.

Responsibilities​

  • Catalog aggregation: fetch and normalize tools/list from configured upstream MCP Servers; publish a consolidated catalog (supports large catalogs with scoped, virtual servers/views).
  • Invocation proxy: route tools/call to the correct upstream; preserve IDs/correlation and response shape.
  • Authentication: perform OAuth On‑Behalf‑Of/Token Exchange to mint audience‑bound upstream tokens; carry Rich Authorization Requests (RAR); optionally require DPoP.
  • Authorization: call the OpenID AuthZEN PDP for every tools/call (single/batch). Subject = delegated agent; Resource = tool; Context = RAR details and runtime attributes. PDP returns boolean only.
  • Observability & audit: emit decision metrics and business logs; correlate requests; forward or deny with concise reasons.

Why it exists (and what it is not)​

  • The ARIA MCP Gateway is the central choke point for MCP authN/Z. All MCP JSON‑RPC/REST must pass through it in production.
  • It is not a tool catalog generator. CRUDService Loopback MCP generates the no‑code tool catalogs and exposes /mcp/* endpoints; the Gateway authorizes and proxies access to them.
  • It is not ARIA Shield (formerly BFF). Human traffic (SPAs) and provider streaming/budgets use ARIA Shield; agent MCP traffic uses the MCP Gateway.

Architecture (high level)​

Production guidance​

  • Configure agents/UIs to call the ARIA MCP Gateway endpoint only. Do not expose CRUDService /mcp/* directly to external clients.
  • Keep Loopback MCP enabled on CRUDService to generate tools; register those upstreams in the Gateway configuration.
  • Treat ARIA Shield and ARIA MCP Gateway as complementary: ARIA Shield for SPA routes and provider streaming/budgets; MCP Gateway for agent MCP routes.

See also​

  • CRUDService — Loopback MCP (no‑code tool catalogs)
  • ARIA Shield — Provider Proxy and MCP Gateway product family (agent and provider traffic)