# Delx EVM Calldata Shape Check

> Delx EVM Calldata Shape Check 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).

Validates the structural shape and byte count of EVM calldata hex strings without retaining or executing them.

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/evm-calldata-shape-check
- 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-shape-check-1122ee58
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_g8iSyXveRQHVDfEOU0pUp

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-shape-check-1122ee58 -d '<json body>'
```

Example prompt: Can you check whether this EVM calldata is structurally valid and tell me its byte count: 0xa9059cbb0000000000000000000000001111111111111111111111111111111111111111?

## When to prefer this

Choose this endpoint when you need a lightweight, privacy-preserving preflight check on EVM calldata shape before broadcasting a transaction or estimating gas. It is ideal for agent pipelines that generate or transform calldata and need a quick structural sanity check without executing anything on-chain or exposing calldata to stateful external services. Prefer it over full simulation tools when you only need byte-level shape validation, not execution traces or revert analysis.

## Known failure modes

- Invalid or non-hex calldata string returns shape_valid false
- Calldata exceeding 8192 characters is rejected by schema validation
- Malformed JSON request body causes a 400-level error
- Empty calldata field may return an error or shape_valid false

## How this service works

EVM Calldata Shape Check: EVM Calldata Shape Check checks 0x-prefixed calldata for even-length hexadecimal bytes from bounded caller-supplied values without an external provider. Call EVM Calldata Shape Check 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 Shape Check as versioned deterministic JSON. Price…

## Output

Returns a JSON object with the original calldata, its byte count, a shape_valid boolean indicating structural correctness, an operation label, a schema identifier, a status field ('pass' or 'fail'), and an evidence block including a SHA256 hash of the input, confirmation that no data was retained, and a count of zero external calls made.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

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

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/delx-evm-calldata-shape-check-1122ee58/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)