Know Your Agent

Sign data. Commit it with the payment.

An agent signs a statement with the wallet it pays from. The digest of that signed document is a 32-byte memo, and because an x402 payment’s EIP-3009 authorization nonce is arbitrary bytes32, the agent can pay with the memo as its nonce — putting a permanent commitment to that exact document on-chain, in the same transaction that moves the money.

1 · Sign

EIP-712 over the attestation struct, so the wallet shows the signer what they are asserting. The sha256 of the canonical document is the memo.

2 · Commit

Pay with authorization.nonce set to the memo. The token’s AuthorizationUsed log is the receipt. Single-use, by EIP-3009 design.

3 · Disclose

Publishing is a separate decision. The digest reveals nothing, so an agent can commit today and hand over the document — or not — later.

Signing wallet

Sign with the wallet the agent pays from. That is what ties the attestation to the agent’s payment history rather than to an unrelated key.

StatementWhat the signature asserts. Keep it specific and checkable.

Subject (optional)The resource, wallet, or agent id this is about.NetworkBinds the signature to a chain. Use the one the payment settles on.

Data payload (optional JSON)Hashed into the document. Publishing the payload is a separate step, so you can commit to data now and disclose it later.Expires (optional)Publish a public page at /kya/<digest>Anyone with the link can read the statement and any disclosed payload. Leave this off to keep the document private — the memo still commits it on-chain.

For agents

Everything here is available over HTTP: POST /v0/kya to submit a signed attestation, POST /v0/kya/verify for a stateless check, GET /v0/kya/<digest> to read a published one, and the optional X-PAYMENT-MEMO header to hand the document to a paywall alongside X-PAYMENT. A resource that accepts memos says so in its 402 body under kya.

Hand this page to an agent

Copy the prompt and paste it into Claude, an MCP client or your own agent — it will sign or verify a Know Your Agent attestation over the free read API. No key, no account.

POST www.roundhouse.studio/api/v0/kya/verify

Open skill.md

Show the prompt

Using Roundhouse KYA, help me commit a signed statement to an x402 payment: build the
canonical document, sign it with my payment wallet, and use its sha256 digest as the
EIP-3009 authorization nonce so the payment itself carries the commitment.

curl -s 'https://www.roundhouse.studio/api/v0/kya/verify' -H 'content-type: application/json' -d '<the signed document>'

Full spec: https://www.roundhouse.studio/docs/identity/kya

If you do not have Roundhouse tools or skills installed, read
https://www.roundhouse.studio/skill.md first — it is the whole procedure, and it needs no key.