# CRC-16 Integrity Checksum

> CRC-16 Integrity Checksum is a paid API for AI agents from checksum.openverbs.com, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).

Computes a CRC-16 checksum for a given data payload, supporting multiple CRC-16 variants (ccitt-false, xmodem, modbus, ibm) and input encodings (utf8, hex, base64).

## Facts

- Endpoint: POST https://checksum.openverbs.com/v1/crc16
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/crc-16-integrity-checksum-27395fb1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_kUBVRWFKSiYwFhSzEZ0mQ

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 crc-16-integrity-checksum-27395fb1 -d '<json body>'
```

Example prompt: Calculate a CRC-16 MODBUS checksum for this UTF-8 string: 'Hello, World!' so I can verify data integrity before transmitting it.

## When to prefer this

Prefer this endpoint when you need a quick, reliable CRC-16 checksum computation without running code locally, especially when working with specific CRC-16 variants like MODBUS for industrial protocols, XMODEM for file transfers, or CCITT for telecommunications. It is particularly useful in agent workflows that need data integrity checks without access to a runtime environment, or when verifying payloads before transmission in embedded or network protocol contexts.

## Known failure modes

- Input data exceeds 5,000,000 character maximum — request rejected
- Invalid encoding specified — must be utf8, hex, or base64
- Invalid CRC-16 variant specified — must be ccitt-false, xmodem, modbus, or ibm
- Malformed base64 or hex input that cannot be decoded
- Missing required 'data' field in the body — returns validation error
- Payment not included or insufficient — x402 payment required error

## How this service works

CRC-16 over the input payload in one of several standard variants (ccitt-false, xmodem, modbus, ibm; default ccitt-false). Returns the checksum as an unsigned integer and 4-digit hex. Non-cryptographic.

## Output

Returns a CRC-16 checksum value computed from the input data using the specified variant (ccitt-false, xmodem, modbus, or ibm) and decoding the input according to the specified encoding (utf8, hex, or base64).

## 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",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "required": [
      "data"
     ],
     "properties": {
      "data": {
       "type": "string",
       "maxLength": 5000000,
       "description": "Input payload."
      },
      "variant": {
       "enum": [
        "ccitt-false",
        "xmodem",
        "modbus",
        "ibm"
       ],
       "type": "string",
       "description": "CRC-16 variant. Default ccitt-false."
      },
      "encoding": {
       "enum": [
        "utf8",
        "hex",
        "base64"
       ],
       "type": "string",
       "description": "How to decode `data`. Default utf8."
      }
     },
     "additionalProperties": false
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/crc-16-integrity-checksum-27395fb1/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from checksum.openverbs.com](https://www.zero.xyz/host/checksum.openverbs.com/llms.txt)