Capmus

Remote MCP server for SUpost, the marketplace for Stanford — and, via BRAND=capmus, for Capmus (capmus.com), which serves the same public API from the same supost-web codebase. One repo, two Vercel projects:

Brand	Vercel project	Endpoint	Env
SUpost	supost-mcp	https://mcp.supost.com/mcp	(defaults)
Capmus	capmus-mcp	https://mcp.capmus.com/mcp	BRAND=capmus

BRAND selects the server name, tool titles/descriptions, and default base URL; SUPOST_BASE_URL still overrides the base URL for previews.

Lets AI agents search active listings, fetch listing details, read verified market statistics, message posters, and create draft listings.

This is doc 190 workstream E3 (see supost-web/docs/dev/190-ai-agent-discovery-implementation-plan.md). It is a pure client of SUpost's public surfaces — the read-only listings API (E2), public listing pages, and /stats.md. It has no privileged database access and holds no secrets; the only configuration is the public base URL.

Tools

Tool	Backing surface	What it returns
search_listings	GET /api/public/listings	Newest-first active listings (id, title, price, category, created_at, canonical URL) with opaque cursor pagination. Params: q, cat, university, max_price, limit (≤50), cursor.
get_listing	GET /post/index/<id> → canonical listing page	One listing incl. full description, parsed from the page's schema.org Product JSON-LD.
get_market_stats	GET /stats.md	The public stats page's markdown rendition (audience, listing volumes, response rates/times).
list_categories	GET /api/public/categories	The active category/subcategory taxonomy — valid create_post values.
create_post	POST /api/public/posts	Creates a DRAFT listing; returns a continue_url where the poster adds photos, reviews, and publishes (paying first when not on the free tier). Never publishes directly.
send_message	POST /api/public/messages	Submits a message to a listing's poster. NOT delivered immediately: a confirmation link is emailed to reply_to_email, and the message only goes out after the human clicks it — agents must report it as pending confirmation, never sent.

No personal information is ever returned. send_message is the supported way to contact a poster; the listing's url also carries the on-site message form. API terms: https://supost.com/api/public/openapi.json.

Hosting

Deployed on Vercel as a stateless streamable-HTTP MCP endpoint (mcp-handler + @modelcontextprotocol/sdk):

https://mcp.supost.com/mcp        (rewritten to /api/mcp)

No sessions, no Redis, no auth — every request is independently served and all upstream data is public and CDN-cached.

Deploy

vercel deploy          # preview
vercel deploy --prod   # production

Optional env var: SUPOST_BASE_URL (default https://supost.com; set to https://preview.supost.com on preview deployments to point at the dev stack).

Connect a client

claude mcp add --transport http supost https://mcp.supost.com/mcp

or in any MCP client that supports remote servers, add the URL above as a streamable-HTTP server.

Rate limiting

The public API enforces ~60 requests/minute/IP and serves 5-minute CDN caching. The client in src/http.ts respects this: on a 429 it honors Retry-After (capped at 5 s), retries once, and otherwise surfaces a structured rate_limited error instructing the agent to back off — it never retries in a loop. All requests carry a supost-mcp/… User-Agent.

Development

npm install
npm run check    # typecheck + tests
SUPOST_BASE_URL=https://preview.supost.com npx tsx scripts/smoke.ts   # live end-to-end

Tests (vitest) cover each tool's request/response mapping, error mapping, JSON-LD extraction, and the rate-limit contract (Retry-After honored, capped, single retry, structured failure).

Follow-ups (manual steps)

• Publish to the MCP registry — server.json is ready. Make the repo public first (gh repo edit Capmus-Team/supost-mcp --visibility public), then: sh brew install mcp-publisher mcp-publisher login github # device flow, needs a browser mcp-publisher publish # from the repo root For the Capmus entry, publish server.capmus.json the same way (cp server.capmus.json server.json in a scratch checkout, or mcp-publisher publish --file server.capmus.json if supported).
• /help/mcp docs page in supost-web — PR #1242 (guide registry entry + llms.txt MCP line); live once merged to dev → master.
• PR/citation announcement — draft and story beats in docs/announcement-draft.md; post after the registry listing and /help/mcp are live (doc 190 workstream F).
• E2 is live on production (supost.com, 2026-07-09); smoke script verified against production, and the server is deployed at https://mcp.supost.com/mcp.