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Agent402 Auto Messages - Pay-Per-Call LLM Inference via x402
x402
Agent402 Auto Messages - Pay-Per-Call LLM Inference via x402 is a paid API for AI agents from agent402.tools, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).
Runs an Anthropic-compatible chat completion (Messages API) against 500+ pay-per-call AI tools, billed at $0.01 USDC per call via the x402 payment protocol — no signup or API key required.
Price / call$0.01
Success—
StatusUnknown
How this service works
Anthropic Messages API over x402 - point the Anthropic SDK (or Claude Code / the Agent SDK) at base_url https://agent402.tools/v1/auto and pay $0.01 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 Messages wire (Claude natively, others translated). Up to 16,000 input chars and 1024 output tokens; streaming supported.
Output
Returns an Anthropic Messages API-compatible JSON object containing the assistant role, one or more content blocks (text or tool_use), the model used, stop reason (end_turn, tool_use, max_tokens, etc.), and a usage object with input and output token counts. When streaming is enabled, returns Anthropic SSE events (message_start through message_stop).
Example use cases
Anonymous LLM call via crypto wallet
“I don't want to create any accounts — just send the message 'Summarize the pros and cons of proof-of-stake consensus' to Claude Sonnet 5 through Agent402, cap the response at 300 tokens, and pay the $0.01 USDC fee from my wallet.”
AI agent calling built-in tools
“Use Agent402's auto tier to ask an AI 'What is the current US CPI inflation rate and what does it mean for bond prices?' — let it use whatever built-in financial tools it needs, and stream the response back to me.”
Extended thinking on a hard reasoning problem
“Run this through Agent402 with Claude's extended thinking enabled and a 5000-token thinking budget: 'Given a 60/40 portfolio of $500k, how should I rebalance after a 20% equity drawdown?' — max output 1000 tokens.”
Technical details
Endpoint
POSThttps://agent402.tools/v1/auto/messagesWhen to prefer
Choose this endpoint when you need Anthropic-compatible LLM inference without creating an account or managing API keys — authentication is handled entirely by a crypto wallet paying $0.01 USDC per call via x402. It is especially suited for AI agents that need to pay programmatically, require zero-data-retention providers, or want to access 500+ built-in pay-per-call tools bundled with the inference layer. Prefer alternatives (direct Anthropic or OpenAI APIs) when you already have API keys, need guaranteed SLAs, or require models outside the Agent402 allowlist.
Side effects
- 402 Payment Required if the x402 payment header is missing or the USDC balance is insufficient
- 400 Bad Request if messages array is missing or malformed
- 400 if max_tokens is missing (required by Anthropic Messages API)
- Model not allowlisted for tier if a disallowed model ID is specified
- Context length exceeded if messages exceed the model's context window
- Rate limiting or capacity errors from the upstream model provider
- Stream connection drop for long SSE responses
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| zdr | boolean | Optional - zero-data-retention providers only |
| model | string | Model id (OpenRouter naming, e.g. anthropic/claude-sonnet-5) - allowlisted per tier; omit (or "auto") on the auto tier |
| tools | array | Optional client tools {name, description, input_schema}; server/built-in tools are not served |
| stream | boolean | Anthropic SSE (message_start … message_stop) |
| system | string | Optional system prompt (string or text blocks) |
| messages | array | Anthropic messages: {role: user|assistant, content: string | [text|image|tool_use|tool_result blocks]} |
| thinking | object | Optional {type:"enabled", budget_tokens} | {type:"adaptive"} | {type:"disabled"} - thinking tokens are output tokens |
| max_tokens | integer | Required by the Messages API; clamped to the tier's output cap |
Output
Schema · Response
{
"type": "json",
"example": {
"id": "msg_…",
"role": "assistant",
"type": "message",
"model": "anthropic/claude-sonnet-5",
"usage": {
"input_tokens": 14,
"output_tokens": 18
},
"content": [
{
"text": "x402 is an HTTP-native way for agents to pay per request with USDC.",
"type": "text"
}
],
"stop_reason": "end_turn"
}
}Tags
x402
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