# Delx Commerce — Content Length Check

> Delx Commerce — Content Length Check is a paid API for AI agents from commerce.delx.ai, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-01).

Verifies whether a declared HTTP Content-Length header value matches the observed byte length of a response body, returning a pass/fail result with a delta.

## Facts

- Endpoint: POST https://commerce.delx.ai/api/v1/x402/content-length-check?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-01
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/delx-commerce-content-length-check-9d01faa4
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_W4P5rT54FlNybUREhU6Dv

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-commerce-content-length-check-9d01faa4 -d '<json body>'
```

Example prompt: Check whether the declared content length of 1024 bytes matches the observed content length of 987 bytes — I want to know if there's a mismatch and what the delta is.

## When to prefer this

Choose this endpoint when you need a verifiable, auditable, pay-per-use check of whether an HTTP Content-Length header matches the actual observed body size — particularly when you need cryptographic evidence (SHA-256 input hash) that no data was retained and no external calls were made. Prefer it over custom validation logic when you want tamper-evident results or when operating in an agent pipeline that requires provable, per-call billing via USDC on Base or Solana.

## Known failure modes

- Missing or non-integer 'declared' or 'observed' fields return a validation error
- Negative integer inputs may be rejected or produce unexpected deltas
- Network or payment failures (x402 protocol) prevent the call from completing
- Malformed request body returns a 4xx error before processing

## How this service works

Pay-per-result APIs for agents. No signup. Exact price. Verifiable delivery. USDC on Base + Solana via x402.

## Output

Returns a JSON object with a boolean 'matched' field, the 'delta' between declared and observed values, the original declared and observed integers, an operation status ('pass'/'fail'), and an evidence block containing a SHA-256 hash of the input, a flag confirming no data retention, and a count of external calls made (always 0).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "declared": {
   "type": "integer",
   "description": "Declared supplied to Content Length Check; used only for this bounded calculation and processed in memory without retention."
  },
  "observed": {
   "type": "integer",
   "description": "Observed supplied to Content Length Check; used only for this bounded calculation and processed in memory without retention."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": {
   "delta": 0,
   "matched": true,
   "declared": 128,
   "observed": 128
  },
  "schema": "delx/util-content-length-check/v1",
  "status": "pass",
  "evidence": {
   "retained": false,
   "input_sha256": "c55f65a8b217d1823723eaaef27fb2baf48c4cfd7f20ccc0fecf75ec925d4da5",
   "external_calls": 0
  },
  "operation": "web_reliability:content_length_check"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/delx-commerce-content-length-check-9d01faa4/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from commerce.delx.ai](https://www.zero.xyz/host/commerce.delx.ai/llms.txt)