The full upstream README, mirrored here for reference. Install config, tool schemas, adoption signals, and an original overview live on the Alienprobe Who MCP listing page.
An MCP server that gives any agent one legal-entity fact — LEI, legal name, jurisdiction, entity and registration status — for $0.05 USDC on Base, paid per call over x402. No signup, no API key, no account. The wallet is the account.
Two tools:
| Tool | Cost | What it does |
|---|---|---|
who_terms | free | Returns the advertised price, network, payee and coverage. Never pays. Works with no wallet. |
who | $0.05, real money | Returns the entity record. Misses and ambiguities cost nothing. |
Three lines. Claude Desktop (claude_desktop_config.json) or Cursor (.cursor/mcp.json):
Drop the env block entirely and the server still starts — who_terms works, who refuses with wallet_not_configured. That is the safe way to try it.
| Var | Default | Meaning |
|---|---|---|
PRIVATE_KEY | (none) | A throwaway Base-mainnet wallet holding a little USDC. Optional. Never logged, echoed, or returned in a tool result. |
MAX_USD_PER_CALL | 0.10 | Hard ceiling on one lookup. The lookup is advertised at $0.05. |
MAX_USD_PER_SESSION | 1.00 | Hard ceiling on everything this server process spends before restart. |
See .env.example. Never commit a real key. Fund a wallet that holds nothing else — about $1 of USDC covers 20 lookups. This repo does not tell you how to get USDC onto Base; see https://docs.base.org/base-chain/tools/bridges/.
The server preflights every who call with a plain, unwrapped fetch — no signer exists on that path — reads the advertised price out of the 402, and only then decides. If the price exceeds MAX_USD_PER_CALL, or would push the running total past MAX_USD_PER_SESSION, it refuses with a result the model can read and act on:
A session is one server process. Restarting the client resets the counter, so the per-session cap is a brake, not a ledger — the wallet balance is the real ceiling. Keep it small.
A paid hit is the API's body verbatim plus paid_usd:
q is a company name, a registrable domain, or a 20-character LEI. To disambiguate a name, append a jurisdiction in the same string: "Acme Corp;US-DE".
paid_usd is the authorized price, not the receiptpaid_usd is the amount the server authorized — the price the API advertised in its 402 and that the spend caps were judged against. It is not read back from the chain.
One case where it overstates: a wallet's first successful lookup on this pricing shelf settles at $0 (first-can-free; a property of the service, not of this client). That call still reports "paid_usd": 0.05. Every subsequent call actually moves $0.05.
The server's session counter inherits the same overstatement, which is the safe direction — it stops you early, never late. If you need the truth, the on-chain USDC Transfer from your wallet is the only receipt. Do not use paid_usd for accounting.
These never pay, and they come back as ordinary tool results the model can reason about — not exceptions:
| Upstream | Result |
|---|---|
400 | {"error":"invalid_subject","reason":"empty"} |
404 | {"error":"not_found","coverage":"..."} |
409 | {"error":"ambiguous","candidates":[...],"hint":"re-ask with the exact legal_name, then a ;jurisdiction suffix if it still collides"} |
503 | {"error":"source_unavailable"} |
The API only charges once it can commit to one entity, so an ambiguous re-ask is still free while it stays ambiguous.
404, not a best-effort answer.npm run smoke hits the live endpoint to fetch the 402. It runs with PRIVATE_KEY blank and asserts the advertised amount is "50000" ($0.05). It cannot pay.
src/core.mjs holds the transport-free logic and takes an injected fetch, which is why the tests never need a wallet. src/index.mjs is only the MCP wiring; @x402/* and viem are imported lazily, on a call already cleared to pay.
Built on @modelcontextprotocol/sdk 1.30.0. See SPEC.md for the full contract and the distribution plan.
MIT © Brent Bryson. See LICENSE.