Sign & Submit API

Synchronous endpoints for signing and submitting transactions directly — no job polling required.

Endpoints

Endpoint	Purpose	Returns
POST /agent/sign	Sign messages, typed data, or transactions	Signature
POST /agent/submit	Submit raw transactions to chain	Transaction hash

POST /agent/sign

Signature Types

Type	Use Case
personal_sign	Plain text messages (auth, verification)
eth_signTypedData_v4	EIP-712 typed data (permits, orders)
eth_signTransaction	Sign transactions for later broadcast

Usage

// personal_sign
const signMessage = await fetch(`${API_URL}/agent/sign`, {
  method: "POST",
  headers: { "x-api-key": API_KEY, "Content-Type": "application/json" },
  body: JSON.stringify({
    signatureType: "personal_sign",
    message: "Sign in to MyApp\nNonce: abc123",
  }),
});
// → { success: true, signature: "0x...", signer: "0x...", signatureType: "personal_sign" }

// eth_signTypedData_v4 (EIP-2612 permit)
const signPermit = await fetch(`${API_URL}/agent/sign`, {
  method: "POST",
  headers: { "x-api-key": API_KEY, "Content-Type": "application/json" },
  body: JSON.stringify({
    signatureType: "eth_signTypedData_v4",
    typedData: {
      domain: { name: "USD Coin", version: "2", chainId: 8453, verifyingContract: "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913" },
      types: {
        Permit: [
          { name: "owner", type: "address" },
          { name: "spender", type: "address" },
          { name: "value", type: "uint256" },
          { name: "nonce", type: "uint256" },
          { name: "deadline", type: "uint256" },
        ],
      },
      primaryType: "Permit",
      message: { owner: "0x...", spender: "0x...", value: "1000000", nonce: "0", deadline: "1735689600" },
    },
  }),
});

// eth_signTransaction
const signTx = await fetch(`${API_URL}/agent/sign`, {
  method: "POST",
  headers: { "x-api-key": API_KEY, "Content-Type": "application/json" },
  body: JSON.stringify({
    signatureType: "eth_signTransaction",
    transaction: { to: "0x...", chainId: 8453, value: "0", data: "0xa9059cbb..." },
  }),
});

Error Responses

Status	Error	Cause
400	Missing required field	Missing message, typedData, or transaction
401	Authentication required	Missing or invalid API key
403	Read-only API key	Key lacks write permissions

POST /agent/submit

Transaction Fields

Field	Type	Required	Description
to	string	Yes	Destination address
chainId	number	Yes	Chain ID (8453=Base, 1=Ethereum, 137=Polygon)
value	string	No	Value in wei
data	string	No	Calldata (hex)
gas	string	No	Gas limit
maxFeePerGas	string	No	EIP-1559 max fee
maxPriorityFeePerGas	string	No	EIP-1559 priority fee

Options

Field	Type	Default	Description
description	string	—	Human-readable description for logging
waitForConfirmation	boolean	true	Wait for on-chain confirmation

Usage

// Submit a transaction and wait for confirmation
const result = await fetch(`${API_URL}/agent/submit`, {
  method: "POST",
  headers: { "x-api-key": API_KEY, "Content-Type": "application/json" },
  body: JSON.stringify({
    transaction: { to: "0x...", chainId: 8453, value: "1000000000000000000" },
    description: "Send 1 ETH",
    waitForConfirmation: true,
  }),
});
// → { success: true, transactionHash: "0x...", status: "success", blockNumber: "123", gasUsed: "21000" }

// Fire-and-forget (don't wait for confirmation)
const pending = await fetch(`${API_URL}/agent/submit`, {
  method: "POST",
  headers: { "x-api-key": API_KEY, "Content-Type": "application/json" },
  body: JSON.stringify({
    transaction: { to: "0x...", chainId: 8453, value: "100000000000000000" },
    waitForConfirmation: false,
  }),
});
// → { success: true, transactionHash: "0x...", status: "pending" }

Multi-Step Workflow

// Approve + Swap sequence
async function approveAndSwap(approveTx: object, swapTx: object) {
  // 1. Approve token spending
  const approval = await submitTransaction(approveTx);
  if (approval.status !== "success") throw new Error("Approval failed");

  // 2. Execute swap
  const swap = await submitTransaction(swapTx);
  if (swap.status !== "success") throw new Error("Swap failed");

  return swap;
}

Transaction Status Values

Status	Description
success	Confirmed and succeeded
reverted	Confirmed but reverted
pending	Submitted, not yet confirmed

Comparison with /agent/prompt

Feature	/agent/prompt	/agent/sign	/agent/submit
Input	Natural language	Structured data	Transaction object
Response	Async (job ID)	Sync (signature)	Sync (tx hash)
Executes on-chain	Via AI agent	No	Yes
Best for	General queries	Auth, permits	Raw transactions

Security Notes

• /agent/submit executes immediately — no confirmation prompt
• Read-only API keys get 403 on both endpoints
• Always validate transaction parameters before submission
• Use waitForConfirmation: true for critical transactions

Related Skills

• bankr-api-basics - API fundamentals
• bankr-client-patterns - Client setup
• bankr-safety - Security best practices
• bankr-arbitrary-transaction - Constructing raw transaction JSON