ISBN Check Digit Validator

Validate a 10- or 13-digit ISBN's check digit (ISO 2108), or compute the check digit a 9- or 12-digit ISBN prefix would need.

Free tier eligible — 500 calls/month with a free key from /pricing; x402 pay-per-call above quota.

Parameters

Parameter	Type	Required	Description
`isbn`	string	required	ISBN (hyphens/spaces allowed)
`mode`	string	optional	validate \| check_digit (default validate) One of: validate, check_digit

Call it over MCP (JSON-RPC 2.0)

curl -s https://wingmanprotocol.com/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc": "2.0", "id": 1, "method": "tools/call", "params": {"name": "isbn_check_digit", "arguments": {"isbn": "example"}}}'

Or plain HTTP

curl -s https://wingmanprotocol.com/tools/isbn_check_digit \
  -H 'Content-Type: application/json' \
  -d '{"isbn": "example"}'

Try it live

Edit the JSON and run it — this POSTs to https://wingmanprotocol.com/tools/isbn_check_digit from your browser.

This tool is x402-metered — agents pay per call with USDC on Base. The 402 response below is the standard x402 payment-requirements envelope: sign the EIP-3009 authorization and retry with the X-Payment header, or get a free key at /pricing (500 calls/month, no card, no crypto).