# Delx Commerce — X402 Delivery Size Check

> Delx Commerce — X402 Delivery Size 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).

Checks whether a result object's serialized byte size falls within a specified budget, returning byte count and pass/fail status without retaining the data.

## Facts

- Endpoint: POST https://commerce.delx.ai/api/v1/x402/x402-delivery-size-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-x402-delivery-size-check-38e7f251
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Q9O5G7cot-uUEGMyYHQkL

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-x402-delivery-size-check-38e7f251 -d '<json body>'
```

Example prompt: Check whether this result object is within a 512-byte budget — just measure it and tell me if it fits without storing anything.

## When to prefer this

Use this endpoint when you need a lightweight, verifiable, privacy-preserving byte-size check on a result object before committing to an x402 delivery — especially when you need cryptographic evidence (SHA-256) that the input was not retained. Prefer this over a local size calculation when auditability and proof-of-no-retention matter, or when operating in an x402 payment pipeline where delivery size constraints must be enforced.

## Known failure modes

- Missing required 'result' field causes validation error
- 'maximum_bytes' not provided may default to unbounded check or return error
- Result object exceeding 128 properties (maxProperties limit) is rejected
- Payment not included or invalid USDC payment causes 402 response
- Malformed JSON body causes 400 parse error

## 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 containing the serialized byte size of the submitted result, a boolean indicating whether it falls within the specified maximum_bytes budget, a pass/fail status string, and an evidence block with SHA-256 hash of the input, a flag confirming no data was retained, and the number of external calls made (always 0).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "result": {
   "type": "object",
   "description": "Result supplied to X402 Delivery Size Check; used only for this bounded calculation and processed in memory without retention.",
   "maxProperties": 128,
   "additionalProperties": true
  },
  "maximum_bytes": {
   "type": "integer",
   "description": "Maximum Bytes supplied to X402 Delivery Size Check; used only for this bounded calculation and processed in memory without retention."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": {
   "bytes": 39,
   "within_budget": true
  },
  "schema": "delx/util-x402-delivery-size-check/v1",
  "status": "pass",
  "evidence": {
   "retained": false,
   "input_sha256": "076621b47df3f39c3106d66269581bbf20cc78094ab64cec4fdb10ac2b5f03d1",
   "external_calls": 0
  },
  "operation": "delivery_contract:x402_delivery_size_check"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/delx-commerce-x402-delivery-size-check-38e7f251/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)