# Delx JSON Contract Check

> Delx JSON Contract Check is a paid API for AI agents from api.delx.ai, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-13).

Validates a JSON payload against a caller-supplied structural contract and returns path-level validation errors

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/json-contract-check
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/delx-json-contract-check-36ff6dc5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_f6p_6APhBTpID3iW842Yy

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-json-contract-check-36ff6dc5 -d '<json body>'
```

Example prompt: Before we process this webhook payload, check it against the contract that requires a top-level 'userId' string, an 'amount' number, and a 'status' field that must be one of 'pending', 'complete', or 'failed' — tell me if anything is missing or wrong.

## When to prefer this

Choose this endpoint when you need deterministic, stateless, path-level JSON validation against a bounded structural contract — especially in autonomous agent pipelines where you need machine-readable error output before acting on untrusted input, retrying a request, or evaluating API reliability. It is ideal when you control both the contract and the instance, need guaranteed local-only execution with no upstream provider calls, and require that invalid payloads do not incur billing. Prefer it over general-purpose schema validators when operating in a pay-per-call x402 environment and when structured error paths matter more than human-readable messages.

## Known failure modes

- Malformed contract schema causes a contract parse error response
- Instance is not valid JSON, resulting in a parse failure
- Missing 'contract' or 'instance' fields in the request body cause a 400-level error
- Payment of $0.002 USDC via x402 not provided or rejected, blocking execution
- Contract uses unsupported schema keywords beyond type/required/properties/enum, which may be silently ignored or flagged

## How this service works

Check a JSON payload against a bounded structural contract and return path-level errors. Use it before an autonomous workflow acts on untrusted input, changes an API, retries a request, or evaluates production reliability. Returns bounded machine-readable JSON for $0.002 USDC via x402 on Base. Execution is deterministic, first-party, local-only, stateless, and does not call an upstream provider; structured validation failures are not billed.

## Output

Returns machine-readable JSON containing a list of path-level validation errors found in the instance against the provided contract. Each error identifies the specific JSON path and the nature of the violation (e.g. missing required field, wrong type, value not in enum). If the payload is fully valid, returns an empty errors list. Structured validation failures are not billed.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "contract": {
   "type": "object",
   "description": "Bounded JSON Schema-like contract using type, required, properties, and enum."
  },
  "instance": {
   "description": "JSON value to check."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "scope": "bounded structural subset: type, required, properties, enum",
  "valid": true,
  "errors": [],
  "schema": "delx/json-contract-check/v1",
  "error_count": 0
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/delx-json-contract-check-36ff6dc5/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)