# SignalHarness ABI Interface Compare

> SignalHarness ABI Interface Compare is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Compares two or more smart contract ABI interfaces to identify differences, incompatibilities, or breaking changes.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/abi_interface_compare/invoke
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/signalharness-abi-interface-compare-806e378c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_cfXaMg3w0cpy7d8Z0rIhC

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-interface-compare-806e378c -d '<json body>'
```

Example prompt: Can you compare these two Solidity contract ABIs and tell me if there are any breaking changes or incompatibilities between them? Here's the old ABI: [...] and the new ABI: [...]

## When to prefer this

Use this endpoint when you need a structured, automated comparison of two smart contract ABIs to detect breaking changes, missing functions, or signature mismatches — particularly before contract upgrades, when auditing protocol changes, or when verifying that an implementation matches a standard interface like ERC-20 or ERC-721.

## Known failure modes

- Malformed or non-JSON ABI input causes parsing failure
- Input exceeds 65536 character limit
- Ambiguous or incomplete ABI definitions yield low-confidence or incomplete comparison
- Invalid ABI format (non-standard structure) may result in warnings or partial analysis
- Network or payment settlement failure returns error status

## 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 structured comparison of the two ABI interfaces, including an 'abi_interface_comparison' narrative result, a list of 'warnings' about incompatibilities or breaking changes, the 'service_id', and an 'evidence_scope' field indicating how the analysis was grounded. Also includes a full receipt with payment and execution metadata.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "replay": false,
  "result": {
   "warnings": [
    "Interface similarity does not prove implementation compatibility."
   ],
   "service_id": "abi_interface_compare",
   "evidence_scope": "caller_supplied_data",
   "abi_interface_comparison": "{\"equal\":true,\"only_left\":[],\"only_right\":[],\"shared\":[\"error:Insufficient(uint256)\",\"event:Changed(address,uint256)\",\"function:balanceOf(address)\"]}"
  },
  "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_interface_compare",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "10000",
   "resultSha256": "5f2e0958d8952252e24956abbb96ac159fc814b87a33b2cf50215adf083a87f3",
   "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-interface-compare-806e378c/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)