# Agent402 Pro Responses - Pay-Per-Call AI Completions via x402

> Agent402 Pro Responses - Pay-Per-Call AI Completions via x402 is a paid API for AI agents from agent402.tools, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-15).

Runs AI chat/completion requests through a pay-per-call OpenAI Responses-compatible endpoint, billed at $0.10 USDC per call via x402 micropayment protocol — no API key required.

## Facts

- Endpoint: POST https://agent402.tools/v1/pro/responses
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent402-pro-responses-pay-per-call-ai-completions-via-x402-d2e31ff9
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_N0kgCXg9P3K4vYsn70Yi3

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 agent402-pro-responses-pay-per-call-ai-completions-via-x402-d2e31ff9 -d '<json body>'
```

Example prompt: Using the Agent402 pay-per-call completions endpoint, send this prompt to gpt-4o-mini and return the response: 'Summarize the key benefits of the x402 payment protocol for AI agents in 3 bullet points.' Stream the response back to me.

## When to prefer this

Choose this endpoint when you need OpenAI-compatible LLM completions without managing API keys or subscriptions — ideal for AI agents that authenticate via crypto wallet using x402 or MPP micropayments. Prefer it over direct OpenAI/Anthropic APIs when you want pay-per-call billing in USDC, anonymous/wallet-based identity, or access to 500+ tool-augmented models through a single endpoint. Also prefer when building agent pipelines that need on-chain payment trails or zero-data-retention options.

## Known failure modes

- Payment not included or insufficient USDC — returns HTTP 402 with payment details
- Model ID not allowlisted for the current tier — returns error indicating invalid model
- Input exceeds max_output_tokens cap for the tier — tokens clamped or rejected
- Malformed input array (invalid role/content structure) — returns validation error
- Network timeout on long reasoning requests — partial SSE stream may be cut off
- Zero-data-retention filter applied but no ZDR-compliant provider available — returns provider error

## How this service works

OpenAI Responses API over x402 - point the OpenAI SDK's responses.create() (or the OpenAI Agents SDK) at base_url https://agent402.tools/v1/pro and pay $0.10 per call in USDC, no API key, no signup. Same models, caps and price as this tier's /chat/completions route; any model here is served through the Responses wire.

## Output

Returns an OpenAI Responses-API-compatible JSON object containing the assistant's reply text, the model used, input/output/total token counts, a response ID, and completion status. When streaming is enabled, returns SSE events (response.created through response.completed) with incremental content chunks.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "zdr": {
   "type": "boolean",
   "description": "Optional - zero-data-retention providers only"
  },
  "text": {
   "type": "object",
   "description": "Optional {format: {type: \"text\"|\"json_schema\"|\"json_object\", ...}}"
  },
  "input": {
   "description": "A string, or an array of input items ({role, content} messages with input_text / input_image parts, function_call, function_call_output)"
  },
  "model": {
   "type": "string",
   "description": "Model id (OpenRouter naming) - allowlisted per tier; omit (or \"auto\") on the auto tier"
  },
  "tools": {
   "type": "array",
   "description": "Optional function tools ({type:\"function\", name, parameters}); server-side tools are not served"
  },
  "stream": {
   "type": "boolean",
   "description": "Responses SSE events (response.created … response.completed)"
  },
  "reasoning": {
   "type": "object",
   "description": "Optional {effort: \"none\"|\"minimal\"|\"low\"|\"medium\"|\"high\"|\"xhigh\"|\"max\"} - reasoning tokens count against max_output_tokens"
  },
  "instructions": {
   "type": "string",
   "description": "Optional system/developer instructions"
  },
  "max_output_tokens": {
   "type": "integer",
   "description": "Optional output cap (clamped to the tier cap)"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "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"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent402-pro-responses-pay-per-call-ai-completions-via-x402-d2e31ff9/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent402.tools](https://www.zero.xyz/host/agent402.tools/llms.txt)