Touchstone MCP

@touchstone/mcp-server

The four-tool MCP server — build1-spec.md §9. get_index is free; get_quote, convert, and verify_receipt are paywalled through Circle's Gateway nanopayments (@circle-fin/x402-batching), settled in USDC.

Transport is Streamable HTTP (POST /mcp), not stdio — x402 is an HTTP-status-code protocol, so a paywalled tool needs an HTTP layer to hang a 402 off. verify_receipt's on-chain read is live (src/settlement/on-chain.ts), reading the real deployed TouchstoneEscrow (data/deployments/base-sepolia.json) — StubSettlementReader (src/settlement/reader.ts) remains for tests and for running the server with no chain configured, the same pattern @touchstone/print's StubAttestationClient uses.

Running it locally (Node/Express)

export TOUCHSTONE_ATTESTATION_KEY=0x...  # signs receipts — a dedicated key, never

TOUCHSTONE_PUBLISHER_KEY, which signs prints and

anchors on-chain and has no business on this

public-facing service

export TOUCHSTONE_SELLER_ADDRESS=0x... # receives USDC payments through Gateway pnpm run start # builds, then listens on $PORT (default 3000)

Both env vars are required and there is no default — the server refuses to start rather than run unconfigured. data/prints/ needs at least one published print (pnpm --filter @touchstone/print run publish-print) before get_index/get_quote/convert have anything real to serve.

Deployed: Cloudflare Workers (mcp.touchstoneassay.com)

The live, public deployment is src/workers/ — a different transport (Hono + Cloudflare's McpAgent, Durable-Object-backed) and a different data-loading layer (KV-cached fetches against this repo's own public GitHub content, since Workers has no filesystem), but the exact same four tools and the exact same paywall logic (../paywall.ts, run through a minimal req/res shim — src/workers/node-shim.ts — rather than reimplemented). See that directory's files for the per-piece reasoning; wrangler.jsonc is the binding/route source of truth.

Security boundary: TOUCHSTONE_PUBLISHER_KEY is never present on this Worker — not as a secret, not as a var, not transitively. The only key is TOUCHSTONE_ATTESTATION_KEY, which signs receipts and nothing else (no anchoring, no transactions, no funds). Every other binding is non-sensitive: a chain name, a public contract address, a public RPC URL, and TOUCHSTONE_SELLER_ADDRESS (the existing escrow treasury address, reused as a payment-receiving address — no private key for it exists on this Worker at all).

Setup, once:

npx wrangler login

npx wrangler kv namespace create PRINTS_CACHE # then paste the id into wrangler.jsonc npx wrangler secret put TOUCHSTONE_ATTESTATION_KEY

Enable Analytics Engine once for the account (dashboard-only, no API/CLI path): https://dash.cloudflare.com/ /workers/analytics-engine — usage logging (src/workers/analytics.ts) degrades to a caught, logged no-op if this isn't done, so it never blocks the rest of the service, but the point of it (adoption evidence — call counts, distinct payer addresses) needs it enabled.

Deploy:

pnpm run deploy   # wrangler deploy

Re-run npx wrangler types after changing any binding in wrangler.jsonc — worker-configuration.d.ts (committed) is generated from it and is what makes Env resolve for agents' McpAgent generic constraint; a stale copy silently breaks this.env inside TouchstoneMcpAgent.

Listing this server

Official MCP registry (registry.modelcontextprotocol.io)

src/manifest/server.json is a schema-valid manifest (verified against static.modelcontextprotocol.io/schemas/2025-09-29/server.schema.json) with remotes: [{ type: "streamable-http", url }] — the URL in it is a placeholder (https://mcp.touchstone-assay.example/mcp, the RFC 2606-reserved .example domain) and must be replaced with the real deployment URL before publishing.

curl -L "https://github.com/modelcontextprotocol/registry/releases/latest/download/mcp-publisher_$(uname -s | tr '[:upper:]' '[:lower:]')_$(uname -m | sed 's/x86_64/amd64/;s/aarch64/arm64/').tar.gz" | tar xz mcp-publisher

mcp-publisher login github mcp-publisher publish

The manifest's name (io.github.petrkrulis2022/touchstone-mcp) is namespaced under GitHub-OAuth ownership — mcp-publisher login github must authenticate as an account matching that namespace, or publishing is rejected.

Smithery, Glama, PulseMCP, mcp.so

Each has its own submission flow (typically: connect the GitHub repo through their dashboard, or a registry-specific manifest file), and none were verified against live documentation while building this package — consult each registry's current docs directly before submitting rather than trusting a summary here that could be stale by the time you read it.