# Base Calldata Decoder

> Base Calldata Decoder 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).

Decodes raw Ethereum calldata on Base network, identifying the function name, selector, and decoded arguments from ABI-encoded transaction input data.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/base_calldata_decode/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/base-calldata-decoder-21e75988
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_OFKxThyG3gz-N4ctgj947

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 base-calldata-decoder-21e75988 -d '<json body>'
```

Example prompt: Can you decode this raw Base transaction calldata for me — '0xa9059cbb0000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000006' — and tell me what function it calls and what the arguments are?

## When to prefer this

Choose this endpoint when you need to decode raw EVM calldata specifically on the Base network (chain IDs 8453 or 84532) and want structured output including function name, selector, and arguments. Prefer this over manual ABI decoding when you need quick, pay-per-call access without managing your own node or ABI libraries. Ideal for agents auditing transactions, debugging failed calls, or inspecting DeFi interactions on Base.

## Known failure modes

- Invalid or malformed calldata hex string returns a decoding error
- Unknown function selector with no ABI provided may result in undecodable output or warnings
- Calldata too long (exceeding 65536 character limit) will be rejected
- Empty or null request_json will fail schema validation
- Non-Base calldata from other networks may decode incorrectly due to network context assumptions

## 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 containing the decoded function name, function selector (e.g. '0xa9059cbb'), decoded argument values, total calldata byte size, Base network context (accepted chain IDs, deposit transaction type, fee model, protocol family), evidence scope, and any warnings if the supplied ABI may be incorrect. Also includes a full receipt with payment ID, execution ID, and result hash.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "replay": false,
  "result": {
   "warnings": [
    "A supplied ABI may be incorrect and decoding does not simulate execution."
   ],
   "service_id": "base_calldata_decode",
   "analysis_json": "{\"args\":[\"0x0000000000000000000000000000000000000002\",\"100\"],\"calldata_bytes\":68,\"function_name\":\"transfer\",\"network_context\":{\"accepted_chain_ids\":[\"8453\",\"84532\"],\"deposit_transaction_type\":\"0x7e\",\"fee_model\":\"L2 execution plus caller-supplied L1 data/operator components\",\"protocol_family\":\"OP Stack\"},\"selector\":\"0xa9059cbb\"}",
   "evidence_scope": "caller_supplied_data",
   "analyzed_network": "base"
  },
  "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": "base_calldata_decode",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "10000",
   "resultSha256": "beff1ae8843f8360a1951a55a31040e9fd3afa3b3da6a0927148c1c534263835",
   "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/base-calldata-decoder-21e75988/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)