# Delx Response Contract Diff

> Delx Response Contract Diff is a paid API for AI agents from api.delx.ai, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-15).

Compares expected and actual top-level response fields and value types, returning a machine-readable JSON diff for contract validation.

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/response-contract-diff
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/delx-response-contract-diff-4ba59b9b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_mQ5FOjsWJ58X1mXe2xz2s

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-response-contract-diff-4ba59b9b -d '<json body>'
```

Example prompt: Compare this expected response shape — {"userId": "string", "score": "number"} — against the actual response I got back — {"userId": 42, "score": 99, "extra": "surprise"} — and tell me what fields are missing, unexpected, or the wrong type.

## When to prefer this

Choose this endpoint when you need a fast, deterministic, stateless preflight check to verify that an API response matches an expected contract schema before downstream processing — especially inside enterprise agent workflows where data integrity, policy compliance, or integration correctness must be confirmed cheaply ($0.003) without retaining any input data. Prefer it over manual schema validation logic or heavier contract testing frameworks when you only need top-level field and type comparison.

## Known failure modes

- Missing 'expected' or 'actual' field in request body returns validation error
- Non-object values for expected or actual cause schema rejection
- Deeply nested field differences beyond top-level are not detected
- Network timeout if the endpoint is temporarily unavailable
- Payment failure via x402 if insufficient USDC balance on Base

## How this service works

Compare expected and actual top-level response fields and value types. Use it as a bounded preflight or analysis step inside an enterprise agent workflow before data, policy, integration, security, or commercial decisions reach production. Returns deterministic machine-readable JSON for $0.003 USDC via x402 on Base. Execution is first-party, local-only, stateless, memory-only, and has no paid upstream or input retention. Results are advisory; the caller remains responsible for authorization and…

## Output

Returns deterministic machine-readable JSON detailing the differences between the expected and actual response objects, including missing fields, unexpected extra fields, and value type mismatches at the top level. The result is advisory and stateless.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "actual": {
   "type": "object",
   "description": "Input field: actual."
  },
  "expected": {
   "type": "object",
   "description": "Input field: expected."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "scope": "top-level structural comparison",
  "schema": "delx/util-response-contract-diff/v1",
  "compatible": false,
  "missing_fields": [
   "ready"
  ],
  "type_mismatches": [
   "id"
  ],
  "unexpected_fields": []
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/delx-response-contract-diff-4ba59b9b/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)