# FarOut Pay-Per-Call LLM Inference (GPT-5.3-Codex)

> FarOut Pay-Per-Call LLM Inference (GPT-5.3-Codex) is a paid API for AI agents from farouter.tech, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Runs chat completions against GPT-5.3-Codex via a pay-per-call gateway using x402/USDC micropayments — no API key or account required.

## Facts

- Endpoint: POST https://farouter.tech/v1/models/gpt-5.3-codex/chat/completions
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/farout-pay-per-call-llm-inference-gpt-5-3-codex-653d0480
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_6I8B0aKWJBhCcEK2D1xiM

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 farout-pay-per-call-llm-inference-gpt-5-3-codex-653d0480 -d '<json body>'
```

Example prompt: Ask GPT-5.3-Codex to write a Python function that parses ISO 8601 timestamps and returns them as UTC datetime objects — pay per call with USDC, no API key needed, cap the output at 512 tokens.

## When to prefer this

Choose this endpoint when an autonomous agent needs LLM inference without pre-registering API keys or maintaining a prepaid balance — ideal for agent-to-agent workflows, prototyping, or ephemeral tasks where pay-per-call USDC micropayments via x402 are preferable to subscription billing. Best for coding and reasoning workloads where GPT-5.3-Codex specifically is desired.

## Known failure modes

- Payment rejected if USDC balance on Base is insufficient or x402 handshake fails
- Invalid model ID returns 400 or empty model list
- messages array missing or empty triggers schema validation error
- max_tokens set too low causes truncated or empty responses
- Streaming (SSE) misconfiguration can cause client-side parsing errors
- Rate limits or upstream model unavailability return 429 or 503

## How this service works

Fixed-price chat completions for gpt-5.3-codex on FarOut: flat $0.001 per call (includes up to 4,000 input + 1,000 output tokens). Rate: $0.063/1M input tokens, $0.504/1M output tokens. Pay with USDC on Base using x402. No API key, no account, no prepaid balance.

## Output

Returns an OpenAI-compatible JSON object with a choices array containing the assistant's reply message and finish_reason, plus a usage object showing prompt_tokens and completion_tokens consumed.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "model": {
   "type": "string",
   "description": "Model id from GET /v1/models, e.g. glm-5.3. No provider prefix."
  },
  "stream": {
   "type": "boolean",
   "description": "SSE streaming."
  },
  "messages": {
   "type": "array",
   "items": {
    "type": "object",
    "required": [
     "role",
     "content"
    ],
    "properties": {
     "role": {
      "enum": [
       "system",
       "developer",
       "user",
       "assistant",
       "tool"
      ],
      "type": "string"
     },
     "content": {}
    },
    "additionalProperties": true
   },
   "minItems": 1,
   "description": "Chat messages, [OI]-compatible {role, content}."
  },
  "max_tokens": {
   "type": "integer",
   "minimum": 1,
   "description": "Output token budget. Drives the quote directly."
  },
  "temperature": {
   "type": "number",
   "maximum": 2,
   "minimum": 0,
   "description": "Sampling temperature."
  },
  "max_completion_tokens": {
   "type": "integer",
   "minimum": 1,
   "description": "Alias of max_tokens (gpt-5.x models)."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "usage": {
   "prompt_tokens": 6,
   "completion_tokens": 8
  },
  "choices": [
   {
    "message": {
     "role": "assistant",
     "content": "Hello! How can I help?"
    },
    "finish_reason": "stop"
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/farout-pay-per-call-llm-inference-gpt-5-3-codex-653d0480/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from farouter.tech](https://www.zero.xyz/host/farouter.tech/llms.txt)