Anthropic-compatible Messages API — pay per token with USDC on Base

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0xe9030014F5DAe217d0A152f02A043567b16c1aBf",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "11000",
    "maxTimeoutSeconds": 300
  }
]

{
  "bazaar": {
    "info": {
      "input": {
        "bodyFields": {
          "max_tokens": {
            "description": "Max output tokens",
            "type": "integer"
          },
          "messages": {
            "description": "Conversation history",
            "type": "array"
          },
          "model": {
            "description": "Anthropic-style model id",
            "type": "string"
          },
          "stream": {
            "description": "Stream response as SSE",
            "type": "boolean"
          },
          "system": {
            "description": "Optional system prompt",
            "type": "string"
          },
          "tools": {
            "description": "Optional tool definitions",
            "type": "array"
          }
        },
        "discoverable": true,
        "method": "POST",
        "type": "http"
      },
      "output": null
    },
    "schema": {
      "properties": {
        "input": {
          "properties": {
            "body": {
              "properties": {
                "max_tokens": {
                  "description": "Max output tokens the model may generate",
                  "type": "integer"
                },
                "messages": {
                  "description": "Conversation history, Anthropic Messages API shape",
                  "type": "array"
                },
                "model": {
                  "description": "Anthropic-style model id (e.g. anthropic/claude-opus-5, anthropic/claude-sonnet-4.6)",
                  "type": "string"
                },
                "stream": {
                  "description": "Stream the response as SSE",
                  "type": "boolean"
                },
                "system": {
                  "description": "Optional system prompt",
                  "type": "string"
                },
                "temperature": {
                  "description": "Sampling temperature 0–1",
                  "type": "number"
                },
                "tools": {
                  "description": "Optional tool definitions for tool use",
                  "type": "array"
                }
              },
              "required": [
                "model",
                "max_tokens",
                "messages"
              ],
              "type": "object"
            }
          },
          "type": "object"
        },
        "output": {
          "properties": {
            "example": {
              "properties": {
                "content": {
                  "type": "array"
                },
                "id": {
                  "type": "string"
                },
                "model": {
                  "type": "string"
                },
                "role": {
                  "type": "string"
                },
                "type": {
                  "type": "string"
                },
                "usage": {
                  "type": "object"
                }
              },
              "type": "object"
            }
          },
          "type": "object"
        }
      },
      "type": "object"
    }
  }
}

curl "https://blockrun.ai/api/v1/messages"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

const res = await fetch("https://blockrun.ai/api/v1/messages");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

import httpx
res = httpx.get("https://blockrun.ai/api/v1/messages")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header