Anthropic Messages API over x402

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). Depth: `effort` (low..max) on Claude 4.7+, thinking.budget_tokens on older Claude. Up to 12,000 input chars and 768 output tokens; streaming supported.

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Endpoint

POST https://agent402.tools/v1/nano/messages

Our checks, last 30 days

Example input (from the provider)

{
  "body": {
    "max_tokens": 256,
    "messages": [
      {
        "content": "Summarize x402 in one sentence.",
        "role": "user"
      }
    ],
    "model": "google/gemini-3.1-flash-lite"
  },
  "bodyType": "json",
  "method": "POST",
  "type": "http"
}

Promised output schema (from the provider)

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "properties": {
    "input": {
      "additionalProperties": false,
      "properties": {
        "body": {
          "properties": {
            "effort": {
              "description": "Optional depth control for Claude 4.7+ (Opus 5, Sonnet 5, Fable 5.1): low | medium | high | xhigh | max, validated against the model's own list (GET /v1/models). Not accepted on Haiku 4.5 and older, which take thinking.budget_tokens instead",
              "type": "string"
            },
            "max_tokens": {
              "description": "Required by the Messages API; clamped to the tier's output cap",
              "type": "integer"
            },
            "messages": {
              "description": "Anthropic messages: {role: user|assistant, content: string | [text|image|tool_use|tool_result blocks]}",
              "type": "array"
            },
            "model": {
              "description": "Model id (OpenRouter naming, e.g. anthropic/claude-sonnet-5) - allowlisted per tier; omit (or \"auto\") on the auto tier",
              "type": "string"
            },
            "stream": {
              "description": "Anthropic SSE (message_start \u2026 message_stop)",
              "type": "boolean"
            },
            "system": {
              "description": "Optional system prompt (string or text blocks)",
              "type": "string"
            },
            "thinking": {
              "description": "Optional {type:\"enabled\", budget_tokens} | {type:\"adaptive\"} | {type:\"disabled\"} - thinking tokens are output tokens. On Claude 4.7+ (Opus 5, Sonnet 5, Fable 5.1) thinking is adaptive and `effort` is the depth control; a budget_tokens value is advisory there",
              "type": "object"
            },
            "tools": {
              "description": "Optional client tools {name, description, input_schema}; server/built-in tools are not served",
              "type": "array"
            },
            "zdr": {
              "description": "Optional - zero-data-retention providers only",
              "type": "boolean"
            }
          },
          "required": [
            "max_tokens",
            "messages"
          ]
        },
        "bodyType": {
          "enum": [
            "json",
            "form-data",
            "text"
          ],
          "type": "string"
        },
        "method": {
          "enum": [
            "POST"
          ],
          "type": "string"
        },
        "type": {
          "const": "http",
          "type": "string"
        }
      },
      "required": [
        "type",
        "method",
        "bodyType",
        "body"
      ],
      "type": "object"
    },
    "output": {
      "properties": {
        "example": {
          "properties": {
            "content": {
              "items": {
                "properties": {
                  "text": {
                    "type": "string"
                  },
                  "type": {
                    "type": "string"
                  }
                },
                "type": "object"
              },
              "type": "array"
            },
            "id": {
              "type": "string"
            },
            "model": {
              "type": "string"
            },
            "role": {
              "type": "string"
            },
            "stop_reason": {
              "type": "string"
            },
            "type": {
              "type": "string"
            },
            "usage": {
              "properties": {
                "input_tokens": {
                  "type": "integer"
                },
                "output_tokens": {
                  "type": "integer"
                }
              },
              "type": "object"
            }
          },
          "required": [
            "id",
            "type",
            "role",
            "model",
            "content",
            "stop_reason",
            "usage"
          ],
          "type": "object"
        },
        "type": {
          "type": "string"
        }
      },
      "required": [
        "type"
      ],
      "type": "object"
    }
  },
  "required": [
    "input"
  ],
  "type": "object"
}

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