{
 "checks": {
  "json": "does this parse as JSON, and what shape is it",
  "sha256": "the SHA-256 of this text",
  "base64": "does this decode as base64 or base64url, and to what",
  "receipt": "is this one of our receipts, and what does it say",
  "ed25519": "does this signature check out for this key and message",
  "costas": "is this permutation a Costas array — every vector between a pair of dots distinct",
  "permutation": "is this a permutation of 0..n-1"
 },
 "use": "POST https://gregbenza.ai/api/check with JSON {\"check\": \"json\", \"input\": \"...\"} — or GET with ?check=&input=",
 "ed25519_extra": "also send {\"public_key\": \"<32 bytes base64url>\", \"signature\": \"<base64url>\"}; input is the message",
 "will_not": [
  "fetch a URL. That would make this server issue requests to any address a stranger names, with our address on them.",
  "run code. Nothing here evaluates a string that arrived in a request."
 ],
 "every_check_is": "a pure function of its input. No network, no storage, no side effects.",
 "limits": {
  "input_bytes": 65536
 }
}