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Agent402 Anthropic Messages API (x402, nano tier)
x402
Agent402 Anthropic Messages API (x402, nano tier) is a paid API for AI agents from agent402.tools, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-14).
Proxy the Anthropic Messages API (Claude models) over x402 micropayment at $0.003 USDC per call, requiring no API key or signup
Price / call$0.003
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/nano and pay $0.003 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 12,000 input chars and 768 output tokens; streaming supported.
Output
Returns a full Anthropic Messages API response object including assistant content blocks (text, tool_use, or thinking), stop reason, model used, and token usage counts. When stream=true, returns Anthropic-compatible SSE events from message_start through message_stop.
Example use cases
Keyless Claude for autonomous agent
“I'm building an agent pipeline that needs to call Claude without managing API keys — can you send the message 'Analyze the risk factors in this contract text' to anthropic/claude-sonnet-5 with a 2048 token cap and pay $0.003 USDC per call from my wallet?”
Streaming Claude response in real time
“Stream a Claude response to my user's question 'What are the top 5 causes of the French Revolution?' using the nano tier with SSE streaming enabled and max 512 tokens.”
Claude with custom tools and thinking
“Call Claude with a tool definition for a web search function and enable extended thinking with a 5000 token budget — the user message is 'Research the latest battery technology breakthroughs and cite your sources', capped at 4096 output tokens.”
Technical details
Endpoint
POSThttps://agent402.tools/v1/nano/messagesWhen to prefer
Choose this endpoint when you need Claude inference without an Anthropic API key or account, want pure pay-per-call pricing at $0.003 USDC with no monthly commitment, or are building an autonomous agent that self-funds its own LLM calls via x402 micropayments. Prefer it over the OpenAI-compatible /chat/completions sibling when your code already uses the Anthropic SDK or Messages API format with multi-turn messages, tool use, or extended thinking blocks.
Side effects
- 402 Payment Required if x402 payment header is missing or wallet has insufficient USDC
- Model not allowlisted on nano tier returns an error
- max_tokens clamped silently to tier output cap
- Invalid message format (missing role or content) returns 400
- Network timeout on long generations with large max_tokens
- ZDR flag set but model provider does not support zero-data-retention
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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