# Zeno Finance Responses API (x402)

> Zeno Finance Responses API (x402) is a paid API for AI agents from api.zeno.finance, paid per call via x402, $0.016025/call, status unknown (last checked 2026-10-15).

OpenAI-compatible Responses API endpoint that accepts a prompt and returns generated text with token usage and cost, settled via x402 micropayment on Base.

## Facts

- Endpoint: POST https://api.zeno.finance/v1/responses?utm_source=zero.xyz
- Price: $0.016025/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/zeno-finance-responses-api-x402-ee54d903
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_SW7Pj_rwp4iLz-2sqNghy

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 zeno-finance-responses-api-x402-ee54d903 -d '<json body>'
```

Example prompt: Send this prompt to the Zeno Finance Responses API using gpt-5.4-pro and up to 512 output tokens: 'Summarize the key risks of investing in early-stage startups in three bullet points.'

## When to prefer this

Choose this endpoint when you need OpenAI-compatible text generation with per-request crypto micropayment settlement on Base via x402, especially for wallet-native agents or applications that cannot hold traditional API subscriptions. Prefer it over standard OpenAI direct access when autonomous agent payment without a credit card or API key subscription is required. The Responses API format (vs Chat Completions) is preferable when using structured instructions and single-turn inference patterns.

## Known failure modes

- Insufficient USDC balance or x402 payment failure — payment not settled, request rejected
- Invalid or unsupported model name — returns error indicating unrecognized model
- Prompt exceeds model context window — returns token limit error
- max_output_tokens set below minimum (1) — validation error
- Rate limiting or provider quota exceeded — 429 or 503 response
- Malformed input JSON — 400 bad request

## How this service works

General-purpose Responses API from api.zeno.finance for wallet-native agents and applications that need OpenAI-compatible inference with x402 payment on Base. Pricing starts at $0.001 and is usage-settled up to a $6 per-request cap. Buyers send prompt or structured input and receive concise JSON with output text, tokens spent, and request cost.

## Output

A JSON object containing the generated output text, the number of tokens consumed (input and output), and the cost of the request in USDC. Pricing is usage-settled between $0.001 and $6 per request.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "input": {
   "type": "string",
   "description": "Prompt or instruction to send to the Responses API."
  },
  "model": {
   "type": "string",
   "description": "Configured model name to run, such as gpt-5.5 or gpt-5.4-pro."
  },
  "instructions": {
   "type": "string",
   "description": "Optional system-style instructions for the response."
  },
  "max_output_tokens": {
   "type": "number",
   "minimum": 1,
   "description": "Maximum number of output tokens to generate."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/zeno-finance-responses-api-x402-ee54d903/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.zeno.finance](https://www.zero.xyz/host/api.zeno.finance/llms.txt)