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Agent402 Metered OpenAI Responses API
x402
Agent402 Metered OpenAI Responses API is a paid API for AI agents from agent402.tools, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).
Drop-in OpenAI Responses API proxy that meters each call via x402 micropayments, billing exact token costs (input + max_output_tokens) at model list price × 1.15, minimum $0.001 USDC
Price / call$0.001
Success—
StatusUnknown
How this service works
OpenAI Responses API billed per request from what the call costs: the 402 quotes exact-BPE input (instructions + input items + tools) plus your max_output_tokens at the model's list price, times 1.15, never under $0.001; an upto (Permit2) or credits buyer settles actual usage under that quote. Point the OpenAI SDK's responses.create(), the OpenAI Agents SDK, or OpenAI Codex CLI's model_providers base_url at https://agent402.tools/v1/metered.
Output
An OpenAI Responses API-compatible response object containing the model's generated text (or function call), token usage counts, and optionally a stream of SSE events (response.created through response.completed). The caller is charged the exact BPE-computed token cost at model list price × 1.15, settled via x402 Permit2 or credits, minimum $0.001 USDC.
Example use cases
Agent fleet with per-call billing
“I'm running an OpenAI Agents SDK fleet and want each agent call to be billed separately in USDC with no upfront subscription — point all agents at the Agent402 metered endpoint using model auto, system prompt 'You are a task routing agent', and let each call settle its own cost.”
Streaming chat with crypto micropayments
“Use the Agent402 metered responses endpoint to stream a gpt-4o reply to my question 'Summarize the history of Byzantine architecture' — cap output at 2048 tokens, enable streaming, and handle the x402 payment automatically.”
Function-calling agent with pay-per-use
“I want to run a function-calling workflow using Claude or GPT via Agent402's metered API — pass my three tool definitions, set reasoning effort to medium, limit output to 512 tokens, and let it charge USDC per call rather than a monthly plan.”
Technical details
Endpoint
POSThttps://agent402.tools/v1/metered/responsesWhen to prefer
Choose this endpoint when you need an OpenAI Responses API-compatible interface with zero upfront cost and per-request USDC billing via x402 micropayments — ideal for AI agents, agent fleets, or CLI tools (OpenAI Codex CLI) that already target the OpenAI SDK but need autonomous on-chain payment settlement. Prefer over direct OpenAI when you want crypto-native billing, multi-model routing under one base_url, or fine-grained cost attribution per agent call without a subscription.
Side effects
- Insufficient USDC balance or Permit2 allowance → 402 Payment Required with quoted cost
- Model id not on allowlist for caller's tier → 400 Bad Request
- max_output_tokens exceeds tier cap → value is clamped silently or rejected
- Malformed input array or unsupported content part type → 422 Unprocessable Entity
- Server-side tools requested → not supported, 400 error
- Upstream model provider timeout → 504 Gateway Timeout propagated
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| zdr | boolean | Optional - zero-data-retention providers only |
| text | object | Optional {format: {type: "text"|"json_schema"|"json_object", ...}} |
| input | — | A string, or an array of input items ({role, content} messages with input_text / input_image parts, function_call, function_call_output) |
| model | string | Model id (OpenRouter naming) - allowlisted per tier; omit (or "auto") on the auto tier |
| tools | array | Optional function tools ({type:"function", name, parameters}); server-side tools are not served |
| stream | boolean | Responses SSE events (response.created … response.completed) |
| reasoning | object | Optional {effort: "none"|"minimal"|"low"|"medium"|"high"|"xhigh"|"max"} - reasoning tokens count against max_output_tokens |
| instructions | string | Optional system/developer instructions |
| max_output_tokens | integer | Optional output cap (clamped to the tier cap) |
Output
Schema · Response
{
"type": "json",
"example": {
"id": "resp_…",
"model": "openai/gpt-4o-mini",
"usage": {
"input_tokens": 14,
"total_tokens": 32,
"output_tokens": 18
},
"object": "response",
"output": [
{
"id": "msg_…",
"role": "assistant",
"type": "message",
"status": "completed",
"content": [
{
"text": "x402 is an HTTP-native way for agents to pay per request with USDC.",
"type": "output_text",
"annotations": []
}
]
}
],
"status": "completed"
}
}Tags
x402
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