feat(mcp): Sim MCP server for the full Sim API

[waleedlatif1]

Summary

• Adds the Sim MCP server: one stateless Streamable HTTP endpoint (/api/mcp, or SIM_MCP_URL on a dedicated host such as mcp.sim.ai/mcp) that exposes the full public v2 API — the same 237 operations and names as the CLI
• Four tools instead of one per operation: search_operations, describe_operation, call_read_operation (GET, read-only annotated), call_write_operation (destructive annotated). Unknown names get closest-match suggestions; wrong tool gets pointed at the right one
• Tool calls dispatch in-process to the real v2 route handlers (generated table from the v2 contracts, bun run generate:mcp-operations, enforced by check:mcp-operations), so auth, OAuth scope, rate limits, validation, use cases, and the error envelope are the route's own — MCP adds no authorization of its own
• Auth: API key (X-API-Key or Bearer) or OAuth. OAuth tokens are RFC 8707 audience-bound to the MCP server; in-process v2 routes accept them via a server-only audience context, while the REST API still rejects them
• OAuth: resource parsing generalized to Search + Sim MCP with per-resource scope families; public client registration can now request api:read/api:write, and publicly registered clients must bind API grants to the Sim MCP resource (operator clients like the CLI unchanged)
• Step-up: a token missing the dispatched operation's declared scope gets HTTP 403 insufficient_scope with resource_metadata, before the tool runs
• Dedicated host routing in proxy.ts: on the MCP host only the endpoint + OAuth metadata are served; the app host stops serving /api/mcp so clients bind to one URL
• Shared MCP route helpers (credential parsing, stateless transport, 405, protected-resource metadata/challenge, tool results) — Sim Search MCP refactored onto them
• describe_operation returns the OpenAPI description plus JSON Schema of params/query/body/headers
• mcp client-info surface on dispatched requests; new MCP docs tab (overview, authentication, tools); SIM_MCP_URL documented

Follow-ups (not in this PR): DNS/ALB for mcp.sim.ai + SIM_MCP_URL in hosted envs; Client ID Metadata Documents in the authorization server; MCP SDK v2 for the 2026-07-28 protocol revision

Type of Change

• New feature

Testing

• Unit/route tests for catalog, dispatch, route handler (end-to-end through a real v2 route), host routing, OAuth resource/authorize/register, protected-resource metadata
• End to end against a local instance with the official MCP SDK client: API key and full OAuth flow (DCR → authorize with resource → consent → token → refresh), audience rejection on REST, read-only step-up 403, table create/rows/delete, error paths, and dedicated-host routing
• bun run lint, type-check, check:audits (all audits), docs-manifest:check pass

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated
docs	Skipped		Sep 18, 2026 10:17pm UTC

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; no new actionable issue remains, and both previous findings are resolved.

Summary

The PR adds a stateless Sim MCP endpoint exposing the public v2 API through searchable read/write operation tools, with in-process route dispatch, OAuth resource binding, API-key support, dedicated-host routing, generated operation metadata, tests, and documentation. Changes since the previous review harden API-key/OAuth token-prefix separation and make dedicated-host matching correctly account for ports.

• Exposes the v2 API through four MCP tools while retaining route-level authentication, authorization, validation, and rate limiting.
• Adds OAuth resource metadata, public client registration, audience-bound grants, and operation-level scope enforcement.
• Adds dedicated MCP host routing, generated operation catalogs, documentation, and extensive route and integration tests.
• Resolves both previous findings: operation classification now follows declared OAuth scope, and dedicated-host requests receive the required CORS handling.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  Client[MCP client] --> Endpoint[Sim MCP endpoint]
  Endpoint --> Auth[API key or OAuth admission]
  Auth --> Catalog[Search or describe operation]
  Auth --> Dispatch[Call read or write operation]
  Dispatch --> Scope[Operation scope check]
  Scope --> Route[v2 route handler]
  Route --> Policy[Authorization, validation, and rate limits]
  Policy --> Result[MCP tool result]

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[waleedlatif1]

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[waleedlatif1]

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[waleedlatif1]

@greptile

[waleedlatif1]

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No issues found across 62 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

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