# Delx EVM Calldata Selector Extract

> Delx EVM Calldata Selector Extract is a paid API for AI agents from api.delx.ai, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).

Extracts the 4-byte function selector from raw EVM transaction calldata and validates its shape.

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/evm-calldata-selector-extract
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/delx-evm-calldata-selector-extract-c6d7e322
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_MhPmnu4WPU12PlCs3CIlx

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 delx-evm-calldata-selector-extract-c6d7e322 -d '<json body>'
```

Example prompt: Extract the function selector from this EVM calldata hex string: 0xa9059cbb0000000000000000000000001111111111111111111111111111111111111111 — tell me the 4-byte selector, total byte count, and whether the shape is valid.

## When to prefer this

Use this endpoint when an AI agent needs to inspect or validate raw EVM calldata before executing or routing a smart contract transaction, especially during preflight checks in automated blockchain workflows. Prefer this over manual parsing when you need a verifiable, auditable result with SHA-256 evidence and no data retention guarantees.

## Known failure modes

- Invalid or non-hex calldata string returns a failed parse result
- Calldata shorter than 4 bytes may result in shape_valid: false
- Input exceeding 8192 character limit may be rejected
- Malformed JSON request body returns HTTP 400

## How this service works

EVM Calldata Selector Extract: EVM Calldata Selector Extract extracts the first four calldata bytes as a selector from bounded caller-supplied values without an external provider. Call EVM Calldata Selector Extract before signing, submitting, replacing, or accepting an EVM/Base transaction assembled from caller-owned data. Returns normalized transaction evidence, calculated budget or shape findings, and a fail-closed preflight status for EVM Calldata Selector Extract as versioned deterministic…

## Output

Returns the original calldata, the extracted 4-byte function selector (e.g. 0xa9059cbb), total byte count, a boolean shape_valid flag indicating whether the calldata is properly formed, plus evidence fields including whether input was retained (always false), the SHA-256 hash of the input, and external call count (always 0).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "calldata": {
   "type": "string",
   "maxLength": 8192,
   "description": "Calldata supplied to EVM Calldata Selector Extract; used only for this bounded calculation and processed in memory without retention."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": {
   "calldata": "0xa9059cbb0000000000000000000000001111111111111111111111111111111111111111",
   "selector": "0xa9059cbb",
   "byte_count": 36,
   "shape_valid": true
  },
  "schema": "delx/util-evm-calldata-selector-extract/v1",
  "status": "pass",
  "evidence": {
   "retained": false,
   "input_sha256": "1048e8d74a53c6ea3249086735deac2cb24ee3dd131a3852df0439253301d8de",
   "external_calls": 0
  },
  "operation": "evm_preflight:evm_calldata_selector_extract"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/delx-evm-calldata-selector-extract-c6d7e322/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.delx.ai](https://www.zero.xyz/host/api.delx.ai/llms.txt)