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x402 Bazaar — EVM Function Selector Encoder
x402
x402 Bazaar — EVM Function Selector Encoder is a paid API for AI agents from api.relai.fi, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).
Computes the 4-byte ABI selector (e.g. 0xa9059cbb) from a Solidity function signature string, paid via x402 micropayment
Price / call$0.01
Success—
StatusUnknown
How this service works
Computes the 4-byte selector for a function signature (e.g. transfer(address,uint256) → 0xa9059cbb). The inverse of the decoder — useful for agents building or matching calldata. Paid via x402: $0.005 in USDC on Base (eip155:8453) to 0x973a31858f4d2125f48c880542da11a2796f12d6. Returns 402 with payment requirements; pay and retry.
Output
Returns the 4-byte hexadecimal function selector (e.g. 0xa9059cbb) derived from the Keccak-256 hash of the provided function signature. Useful for constructing or matching EVM calldata. Accessed via x402 micropayment flow: first call returns HTTP 402 with payment instructions, client pays $0.005 USDC on Base, then retries to receive the selector.
Example use cases
Example prompt
“What's the 4-byte ABI selector for the Solidity function signature transfer(address,uint256)?”
Technical details
Endpoint
POSThttps://api.relai.fi/relay/1782567677091/api/x402/encode-selectorWhen to prefer
Use this endpoint when an AI agent needs to dynamically compute or verify EVM function selectors for calldata construction, ABI matching, or smart contract interaction — especially when you need the inverse of a selector decoder. Prefer this over offline Keccak hashing when operating in an agentic context that already supports x402 micropayments on Base.
Side effects
- Invalid or malformed function signature returns an error
- Missing or incorrect x402 payment header returns HTTP 402 with payment requirements
- Payment to wrong address or wrong chain (not eip155:8453) may result in failed payment verification
- Signature with unsupported Solidity types may produce unexpected results
- Network timeout on relai.fi relay layer
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object |
Tags
x402
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