# SignalHarness ABI Signature Selector

> SignalHarness ABI Signature Selector is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-13).

Resolves and returns ABI function/event signature selectors for a given Solidity ABI signature request string

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/abi_signature_selector/invoke
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/signalharness-abi-signature-selector-4d7bbb20
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_wt4UL9Py_Fd812ToEVt21

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability signalharness-abi-signature-selector-4d7bbb20 -d '<json body>'
```

Example prompt: What's the 4-byte ABI selector for the Solidity function signature `transfer(address,uint256)`? I need the hex selector I can use when building a raw EVM calldata payload.

## When to prefer this

Choose this endpoint when you need a fast, reliable resolution of Solidity ABI function or event signature selectors without running a local Ethereum node or relying on free public databases that may be incomplete. It is priced per-call at $0.005 USDC via x402 micropayment, making it suitable for agent workflows that need on-demand selector resolution without bulk subscription commitments.

## Known failure modes

- Malformed or syntactically invalid ABI signature string returns error or empty selectors
- Ambiguous overloaded signatures may produce warnings
- Input string exceeding 65536 characters is rejected by schema validation
- Network or payment processing failure returns non-succeeded status
- Unknown or non-standard signature not in known databases may return no match

## How this service works

Explore 330 pay-per-call x402 API services and 27 agent-native digital products, with Base USDC pricing, secure Polar checkout, and free discovery.

## Output

Returns a JSON object with a `signature_selectors` field containing the resolved hex selector(s) for the provided ABI signature, along with any `warnings` about ambiguity or issues, the `service_id`, and `evidence_scope`. Also includes a full payment receipt with timing, payment ID, amount, network (Base), and a SHA256 hash of the result for verification.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "abi_signature_request": {
   "type": "string",
   "maxLength": 65536,
   "minLength": 2
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "replay": false,
  "result": {
   "warnings": [
    "Selectors alone do not prove an interface is implemented."
   ],
   "service_id": "abi_signature_selector",
   "evidence_scope": "caller_supplied_data",
   "signature_selectors": "{\"kind\":\"function\",\"selectors\":[{\"selector\":\"0x70a08231\",\"signature\":\"balanceOf(address)\"},{\"selector\":\"0xa9059cbb\",\"signature\":\"transfer(address,uint256)\"}]}"
  },
  "status": "succeeded",
  "receipt": {
   "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
   "usage": [],
   "status": "succeeded",
   "network": "eip155:8453",
   "artifacts": [],
   "endedAtMs": 0,
   "latencyMs": 0,
   "paymentId": "example-payment",
   "receiptId": "example-receipt",
   "requestId": "example-request",
   "serviceId": "abi_signature_selector",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "5000",
   "resultSha256": "2985fc2ce0e1ecaffce7ea49fbebe23b6adda9e99e9042990c1b32bda229d377",
   "serviceVersion": "1.0.0",
   "settlementReference": "0x0000000000000000000000000000000000000000000000000000000000000000"
  },
  "artifacts": [],
  "requestId": "example-request",
  "executionId": "example-execution"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/signalharness-abi-signature-selector-4d7bbb20/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from signalharness.ai](https://www.zero.xyz/host/signalharness.ai/llms.txt)