# NPI Format Validator (Offline Check Digit)

> NPI Format Validator (Offline Check Digit) is a paid API for AI agents from medical-codes.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).

Validates the format and Luhn check digit of a US National Provider Identifier (NPI) without performing a live registry lookup

## Facts

- Endpoint: GET https://medical-codes.x402tookit.com/npi-check?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/npi-format-validator-offline-check-digit-4b9c7fd2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_f7bEb729BB9KHVwaWqWXZ

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 npi-format-validator-offline-check-digit-4b9c7fd2
```

Example prompt: Can you check if the NPI number 1234567893 has a valid format and correct check digit — I just need an offline format validation, not a live registry lookup.

## When to prefer this

Choose this endpoint when you need fast, cheap, offline NPI format and check-digit validation without incurring the latency or cost of a live NPPES registry lookup. Ideal for pre-validation pipelines, form input checking, or bulk data cleaning where existence confirmation is not required.

## Known failure modes

- Missing or empty 'npi' query parameter returns an error
- NPI not exactly 10 digits returns invalid verdict with reasons
- Non-numeric characters cause format failure
- Service does not confirm provider exists in any registry — only format is checked

## How this service works

Validate a US National Provider Identifier (NPI) format and check digit offline; it does not look up the provider.

## Output

Returns a verdict (valid/invalid), the computed check digit, the meaning of the first digit, a human-readable summary, a list of reasons for the verdict, any fields not checked, a disclaimer noting this is offline-only, and an asOf timestamp with source information.

## 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": [
      "npi"
     ],
     "properties": {
      "npi": {
       "type": "string",
       "description": "10-digit NPI"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "npi": {
       "type": [
        "null",
        "string"
       ]
      },
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "checkDigit": {
       "type": [
        "null",
        "string"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "firstDigitMeaning": {
       "type": [
        "null",
        "string"
       ]
      }
     }
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/npi-format-validator-offline-check-digit-4b9c7fd2/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from medical-codes.x402tookit.com](https://www.zero.xyz/host/medical-codes.x402tookit.com/llms.txt)