Verify API (hosted)

A signed-inference receipt is fully self-verifying — anyone holding the SDK can re-check the five integrity properties locally via verifyReceipt. This page covers the hosted path: https://verify.vdmnexus.com, a stateless service that runs verifyReceipt on the server and returns a verdict signed by a separate Verify operator key.

Use the hosted path when you'd rather POST a JSON blob than embed tweetnacl, bs58, and a Solana RPC client. The local path remains the trust-minimized option.

Endpoint

POST https://verify.vdmnexus.com/api/verify
Content-Type: application/json

No auth. No rate limit in v0.1. Stateless — every request stands alone.

Request

type VerifyRequest = {
  receipt: NexusReceipt;
  prompt: ChatMessage[];
  response: OpenAIChatCompletion;
  endpoint?: string;     // default "https://nexus.vdmnexus.com" — where to fetch the Nexus operator key from
  operatorKey?: string;  // optional base58 pin; skips the endpoint fetch
  rpc?: string;          // optional Solana RPC override
};

NexusReceipt, ChatMessage, and OpenAIChatCompletion are exported by @vdm-nexus/x402. Their shapes are defined in Receipt structure.

Response

type VerifyResponse = {
  v: 1;
  ok: boolean;
  checks: {
    prompt_hash_ok: boolean;
    response_hash_ok: boolean;
    nexus_signature_ok: boolean;
    payment_on_chain_ok: boolean;  // vacuously true for prepaid receipts
    payer_matches: boolean;        // vacuously true for prepaid receipts
  };
  receipt_signature: string | null; // mirrors the input receipt.nexus_signature
  verified_at: number;              // unix ms
  verifier_pubkey: string;          // base58 Ed25519
  verifier_signature: string;       // base58 Ed25519 — see "chain of trust" below
};

Curl

curl -X POST https://verify.vdmnexus.com/api/verify \
  -H "content-type: application/json" \
  -d '{
    "receipt":  { "v": 2, "agent_pubkey": "...", "...": "..." },
    "prompt":   [{ "role": "user", "content": "Hello." }],
    "response": { "id": "...", "object": "chat.completion", "...": "..." }
  }'

Error responses

Error responses do not include verifier_signature.

Operator key

The Verify operator key is separate from the Nexus receipt operator key. Two services, two keys.

curl https://verify.vdmnexus.com/api/verify/operator-key
# { "pubkey": "<base58>", "algorithm": "ed25519", "encoding": "base58" }

Pin this in your downstream consumers so they can re-verify a VerifyResponse independently — without needing to call Nexus Verify again.

Chain of trust

There are two signatures in play. Don't confuse them.

The verify response includes receipt_signature (the receipt's own nexus_signature, or null for v=1 receipts) inside its signed payload. That binding is load-bearing: without it, a signed { ok: true, checks: { ...all true } } blob could be replayed as "proof" that some other receipt verified. Re-verifiers should check that receipt_signature in the verdict matches the nexus_signature on the receipt they hold.

A downstream system can therefore accept a Nexus Verify response, re-check verifier_signature against the published verifier pubkey, and trust the verdict without itself running the on-chain check or re-fetching the Nexus operator key. That's the whole point of publishing the verifier key.

Hosted vs. local

When in doubt, run verifyReceipt locally. This service is convenience, not the source of truth.