# JSON String Length Check

> JSON String Length Check is a paid API for AI agents from api.delx.ai, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-19).

Validates selected string fields in a JSON object against caller-supplied minimum and maximum length bounds, returning counts and normalized validation findings.

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/json-string-length-check?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-19
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/json-string-length-check-9a9ff4c0
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_qg_RlKaIlHjIdIplVr_fI

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-string-length-check-9a9ff4c0 -d '<json body>'
```

Example prompt: Before sending this payload to the downstream tool, check the 'name', 'description', and 'summary' fields to make sure they're all between 5 and 200 characters long.

## When to prefer this

Use this endpoint when an agent needs a deterministic, stateless preflight check on string field lengths in a JSON object before handing structured data to a downstream tool or API with strict character constraints. Prefer it over manual checks when you need versioned, auditable validation findings with normalized output rather than a simple boolean.

## Known failure modes

- Field names listed in 'fields' not found in the provided object — those fields may be skipped or flagged as missing
- Minimum greater than maximum causes an invalid bounds error
- Object exceeds 128 properties limit — request rejected
- Fields array exceeds 256 items — request rejected
- Individual string values exceeding 8192 characters may be truncated or rejected
- Non-string field values may be ignored or cause type mismatch findings

## How this service works

JSON String Length Check: JSON String Length Check checks selected string fields against caller length bounds from bounded caller-supplied values without an external provider. Call JSON String Length 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 String Length Check as versioned deterministic JSON. Price: $0…

## Output

Returns a versioned deterministic JSON object with per-field validation findings, character counts, normalized values, and an overall pass/fail status indicating which fields satisfy the supplied minimum and maximum length bounds.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "fields": {
   "type": "array",
   "items": {
    "type": "string",
    "maxLength": 8192
   },
   "maxItems": 256,
   "description": "Fields supplied to JSON String Length Check; used only for this bounded calculation and processed in memory without retention."
  },
  "object": {
   "type": "object",
   "description": "Object supplied to JSON String Length Check; used only for this bounded calculation and processed in memory without retention.",
   "maxProperties": 128,
   "additionalProperties": true
  },
  "maximum": {
   "type": "integer",
   "description": "Maximum supplied to JSON String Length Check; used only for this bounded calculation and processed in memory without retention."
  },
  "minimum": {
   "type": "integer",
   "description": "Minimum supplied to JSON String Length 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-string-length-check/v1",
  "status": "pass",
  "evidence": {
   "retained": false,
   "input_sha256": "e61f8b4c6194a85d31be821c7ddcec01a240fe3d4b33cd76336131c6315185b6",
   "external_calls": 0
  },
  "operation": "data_batch:json_string_length_check"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/json-string-length-check-9a9ff4c0/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)