# Agent Missing Field Checker

> Agent Missing Field Checker is a paid API for AI agents from agent-product-normalizer.vercel.app, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-18).

Validates a JSON tool call or structured request against a list of required fields and reports which fields are missing

## Facts

- Endpoint: GET https://agent-product-normalizer.vercel.app/api/v1/missing-fields
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-18
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent-missing-field-checker-a5097b2e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_D7KEJpHFcqwh0bdxPN0yv

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 agent-missing-field-checker-a5097b2e
```

Example prompt: Before I call the booking tool, check whether this JSON object is missing any required fields — the required ones are 'name', 'date', 'location', and 'party_size': {"name": "Alice", "date": "2025-06-01"}

## When to prefer this

Choose this endpoint when an AI agent needs to validate a structured JSON payload or tool call before execution — particularly in multi-step agentic workflows where missing fields would cause downstream failures. It is ideal as a pre-flight check before calling external APIs, submitting forms, or passing data between agent steps. Prefer it over generic JSON schema validators when you want a lightweight, per-call check focused specifically on field presence.

## Known failure modes

- Malformed JSON string in the input parameter causes a parse error
- Required fields list is empty or incorrectly formatted, returning no meaningful results
- Input JSON exceeds the 12,000 character limit and is rejected
- Required_fields parameter exceeds the 2,000 character limit
- Network timeout on the Vercel serverless function
- Fields with nested paths may not be detected if only top-level keys are checked

## How this service works

Check whether a tool call or structured request is missing required input fields

## Output

Returns an indication of which required fields are absent from the provided JSON object, allowing the agent to identify gaps before proceeding with a tool call or API request. Typically includes a list of missing field names and may indicate overall validity.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "input",
      "required_fields"
     ],
     "properties": {
      "input": {
       "type": "string",
       "maxLength": 12000,
       "description": "JSON object as a string"
      },
      "required_fields": {
       "type": "string",
       "maxLength": 2000,
       "description": "Comma-separated required field names"
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent-missing-field-checker-a5097b2e/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent-product-normalizer.vercel.app](https://www.zero.xyz/host/agent-product-normalizer.vercel.app/llms.txt)