# JSON Unique Fields Check

> JSON Unique Fields 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).

Detects duplicate composite keys across an array of JSON objects based on a caller-specified set of field names

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/json-unique-fields-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/json-unique-fields-check-5183f038
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Bh1cp5cMxZnYq5gVeO5B7

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 json-unique-fields-check-5183f038 -d '<json body>'
```

Example prompt: Check these 50 user records for duplicate combinations of 'email' and 'org_id' — I need to know which rows share the same composite key before I send the batch to the downstream service.

## When to prefer this

Use this endpoint when you need a lightweight, stateless, pay-per-call composite key uniqueness check on a bounded JSON array without standing up a database or external deduplication service. It is ideal as a pre-flight validation step before handing structured data to a downstream tool with strict uniqueness contracts. Prefer it over full ETL deduplication pipelines when your dataset is small (≤256 rows) and you need a deterministic, versioned result immediately.

## Known failure modes

- Items array exceeds 256 elements — request will be rejected or truncated
- More than 128 properties per object — exceeds maxProperties limit
- Field names reference keys that don't exist in the objects — may return no duplicates or empty results
- Malformed JSON in items — request will fail with a parse error
- Empty items array or empty fields array — returns no findings
- Fields array exceeds 256 entries — request rejected

## How this service works

JSON Unique Fields Check: JSON Unique Fields Check finds duplicate composite keys across object rows from bounded caller-supplied values without an external provider. Call JSON Unique Fields Check before an agent hands structured data or a batch plan to a downstream tool with a stricter contract. Returns the bounded transformation or validation finding with counts, normalized values, and a versioned result contract for JSON Unique Fields Check as versioned deterministic JSON. Price: $0.001 USDC…

## Output

Returns a versioned deterministic JSON result containing: counts of duplicate composite key occurrences, the normalized values of the duplicate keys found, an indication of which rows are affected, and a versioned result contract — all computed in-memory without data retention.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "items": {
   "type": "array",
   "items": {
    "type": "object",
    "maxProperties": 128,
    "additionalProperties": true
   },
   "maxItems": 256,
   "description": "Items supplied to JSON Unique Fields Check; used only for this bounded calculation and processed in memory without retention."
  },
  "fields": {
   "type": "array",
   "items": {
    "type": "string",
    "maxLength": 8192
   },
   "maxItems": 256,
   "description": "Fields supplied to JSON Unique Fields Check; used only for this bounded calculation and processed in memory without retention."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": {
   "unique": true,
   "duplicate_indices": []
  },
  "schema": "delx/util-json-unique-fields-check/v1",
  "status": "pass",
  "evidence": {
   "retained": false,
   "input_sha256": "9add83ab55b011d3994b700af703d6cc08072afb22cf6873ea05add8e1af633e",
   "external_calls": 0
  },
  "operation": "data_batch:json_unique_fields_check"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/json-unique-fields-check-5183f038/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)