# JSON Pattern Fields Check

> JSON Pattern 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).

Validates selected string fields of a JSON object against a caller-supplied regular expression, returning match counts and normalized values in a versioned deterministic result.

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/json-pattern-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-pattern-fields-check-c09325b4
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Pv3_lNmfJzO-edYdajqiu

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-pattern-fields-check-c09325b4 -d '<json body>'
```

Example prompt: Before I send this order JSON to the fulfillment API, check that the fields 'sku' and 'trackingCode' both match the pattern '^[A-Z]{2}\d{6}$' — give me the match counts and any values that fail.

## When to prefer this

Use this endpoint when an agent needs to validate one or more string fields within a JSON object against a known regular expression before passing structured data to a downstream tool with a strict schema contract. It is especially useful for pre-flight checks in agentic pipelines where field format compliance must be confirmed deterministically without calling an external provider or storing data.

## Known failure modes

- Pattern exceeds maxLength of 8192 characters — request rejected
- Object has more than 128 properties — request rejected
- Fields array exceeds 256 items — request rejected
- Invalid regular expression syntax causes pattern compilation failure
- Named fields not found in the object result in zero-match findings
- Payment not included or insufficient USDC — 402 response

## How this service works

JSON Pattern Fields Check: JSON Pattern Fields Check checks selected string fields against a bounded regular expression from bounded caller-supplied values without an external provider. Call JSON Pattern 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 Pattern Fields Check as versioned deterministic JSO…

## Output

Returns a versioned deterministic JSON object containing match counts per field, normalized field values, and a validation finding summary indicating which fields passed or failed the supplied regular expression pattern.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": {
   "passed": true,
   "invalid_fields": []
  },
  "schema": "delx/util-json-pattern-fields-check/v1",
  "status": "pass",
  "evidence": {
   "retained": false,
   "input_sha256": "76c212959ee62ae10d1069f1f04a0f1ac36073c0c300552b25ad1c9929a1bd35",
   "external_calls": 0
  },
  "operation": "data_batch:json_pattern_fields_check"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/json-pattern-fields-check-c09325b4/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)