# FairSeal VDF Random Number Generator

> FairSeal VDF Random Number Generator is a paid API for AI agents from x402.fairseal.io, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).

Returns a cryptographically verifiable random number backed by a Wesolowski 2048-bit Verifiable Delay Function (VDF), served from a pool for sub-2ms latency.

## Facts

- Endpoint: GET https://x402.fairseal.io/v1/rng/latest
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fairseal-vdf-random-number-generator-d44d7cb2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_CU3L6tbaVG0dVYejGLn2A

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 fairseal-vdf-random-number-generator-d44d7cb2
```

Example prompt: Give me a cryptographically verifiable random number right now — one that comes with a VDF proof so I can confirm it hasn't been manipulated.

## When to prefer this

Choose this endpoint when you need randomness that is publicly auditable and cryptographically verifiable — especially for lotteries, games, NFT mints, or smart contracts where trust in the RNG is critical. The VDF proof distinguishes it from standard PRNGs or simple HTTPS-served random numbers that lack auditability. Prefer it over raw OS/library entropy when stakeholders must be able to independently verify fairness post-hoc.

## Known failure modes

- Pool unavailability causes delayed or missing response
- Payment of 0.001 USDC not received results in 402 Payment Required
- Rate limiting or pool exhaustion may cause transient errors
- Malformed or missing x402 payment header results in authentication failure

## How this service works

Verifiable random numbers with cryptographic epoch references. Wesolowski 2048-bit VDF epoch chain with on-chain MerkleAnchor reference. For unbiased randomness: POST /v1/rng/commit (free), then GET the reveal_url returned in the response. Do not construct reveal paths yourself.

## Output

A cryptographically verifiable random number accompanied by a Wesolowski VDF proof (2048-bit), confirming the entropy was generated through a verifiable delay function and cannot be predicted or manipulated retroactively.

## 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",
     "properties": {}
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fairseal-vdf-random-number-generator-d44d7cb2/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402.fairseal.io](https://www.zero.xyz/host/x402.fairseal.io/llms.txt)