Bankr Agent - Sign & Submit API

Sign & Submit API

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

Overview

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

Unlike /agent/prompt (async with job polling), these endpoints return immediately.

POST /agent/sign

Sign data without broadcasting to the network.

Signature Types

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

Prompt Examples

Sign a message:

• "Sign this message: Hello World"
• "Sign in to MyApp with nonce abc123"

Sign typed data (EIP-712 permit):

• "Sign this EIP-712 permit for USDC approval"

Sign a transaction without broadcasting:

• "Sign this transaction but don't send it"

Success Response

{
  "success": true,
  "signature": "0x...",
  "signer": "0xYourWalletAddress",
  "signatureType": "personal_sign"
}

Common Errors

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

Submit raw transactions directly to the blockchain.

Transaction Fields

Field	Required	Description
to	Yes	Destination address
chainId	Yes	Chain ID (8453=Base, 1=Ethereum, 137=Polygon)
value	No	Value in wei (as string)
data	No	Calldata (hex string)
gas	No	Gas limit
waitForConfirmation	No	Wait for on-chain confirmation (default: true)

Prompt Examples

Submit a raw transaction:

• "Submit this transaction on Base: {to: 0x..., data: 0x..., value: 0}"

Simple ETH transfer:

• "Submit a transfer of 1 ETH to 0x..."

Success Response

With confirmation:

{
  "success": true,
  "transactionHash": "0x...",
  "status": "success",
  "blockNumber": "12345678",
  "gasUsed": "21000",
  "signer": "0xYourWalletAddress",
  "chainId": 8453
}

Transaction Status Values

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

Use Cases

• Authentication: Sign messages to verify wallet ownership
• Gasless approvals: Sign EIP-2612 permits without gas
• Pre-built transactions: Submit calldata from external tools
• Multi-step workflows: Execute approve + swap in sequence

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 with no confirmation prompt
• Validate all transaction parameters before submission
• Use waitForConfirmation: true for important transactions
• Read-only API keys cannot use these endpoints (403)