{"name":"MERCURY x402 web-fetch content attestation","keyId":"mercury-x402-attestation-v1:0xACB40253BD71Bb9a5d491b2c6EFF755F2A33Fc75","address":"0xACB40253BD71Bb9a5d491b2c6EFF755F2A33Fc75","alg":"EIP-191-personal_sign","domain":"mercury-x402","ephemeral":false,"messageTemplate":"mercury-x402:fetch-attestation:v1\nurl=<final url>\nstatus=<upstream http status>\nsha256=<0x… sha256 hex of `text`>\nfetchedAt=<iso8601>\nnonce=<0x… 16 random bytes>","howToVerify":"1) recompute sha256(response.text) → must equal attestation.contentHash. 2) reconstruct the message from the template using the response fields. 3) EIP-191 ecrecover the signature over that message → must equal this address. No call back to MERCURY is needed; the receipt is portable + verifiable forever.","note":"Durable key pinned via MERCURY_ATTESTATION_PK.","verifyEndpoint":"/x402/verify"}