Use Recta from an agent wallet: Sign-In-With-X and delegated permissions
For agents that already have a wallet (an EOA, a smart account on Base, MetaMask Agent Wallet, a Coinbase CDP account) or spend from a user's account through a permission: how to sign Recta's request with a standard Sign-In-With-X message, and how to move funds a permission lets you spend.
Sign the request as a Sign-In-With-X message
Recta asks every evaluation to be signed by the address that moves the funds. Wallets that already sign Sign-In-With-X (EIP-4361) messages, as x402 sites ask, can sign Recta's request the same way, without Recta's own text format:
- 1. Send the evaluation unsigned:
POST https://api.recta.build/v1/golden-corridor/commercial-evaluationswith anIdempotency-Keyheader and your body (itssenderis your address). The 401 answer carriessign_in_with_x.message_to_signandsign_in_with_x.payload_without_signature, and the free trial's result. - 2. Sign
message_to_signexactly as given, newlines included, with EIP-191 personal_sign, within 5 minutes. With MetaMask Agent Wallet:mm wallet sign-message --chain-id 8453 --message "<the text>"; with a Coinbase CDP account: itssignMessage; with viem:account.signMessage({ message }). - 3. Add
signaturetopayload_without_signature, encode the JSON in base64 and resend the SAME request (same URL, Idempotency-Key and body bytes) with the headerSIGN-IN-WITH-X: <base64>.
The message names the method, the URL, the Idempotency-Key, the hash of the body, Base (chain id 8453) and a 5-minute window. A different body or key needs a new message: send it unsigned again. A smart account on Base signs it through its owner and is checked by ERC-1271; its transfer must then start on Base.
Then execute and report as usual
The signed answer is the decision. Its execution artifact holds the exact transactions to send from the same address; a wallet with a policy (MetaMask Agent Wallet, a CDP policy) may ask its owner to approve the first transaction to a contract it has not seen. Every later request about that decision (its artifact, fee authorization and execution report) is signed the same way; when its 401 has no message_to_sign (a read names no sender), build the message from sign_in_with_x.info with your own address, as any EIP-4361 library or createSIWxPayload of @x402/extensions does. Details: llms.txt.
Spending through a permission (ERC-7715, Spend Permissions)
If your agent spends from a user's account through a permission, such as MetaMask Advanced Permissions (ERC-7715 and ERC-7710) or Spend Permissions on Base, Recta does not act on the delegation. Move the USDC the permission allows into your agent's own account first, then ask Recta with that account as sender and sign with it. The saving, the route and the 5 % fee are then all your agent's own.