{
  "openapi": "3.0.3",
  "info": {
    "title": "Claude Messages API",
    "version": "1.0.0",
    "description": "Anthropic-compatible Messages API, exposed through AIsa. Send structured messages and generate responses using Claude models."
  },
  "servers": [
    {
      "url": "https://api.aisa.one/v1"
    }
  ],
  "security": [
    {
      "BearerAuth": []
    }
  ],
  "components": {
    "securitySchemes": {
      "BearerAuth": {
        "type": "http",
        "scheme": "bearer",
        "bearerFormat": "AISA API Key",
        "description": "Your AIsa API key as a Bearer token."
      }
    }
  },
  "paths": {
    "/messages": {
      "post": {
        "summary": "Create a message",
        "description": "Send a structured conversation to a Claude model and receive a response. Compatible with the Anthropic Messages API.",
        "operationId": "createMessage",
        "security": [
          {
            "BearerAuth": []
          }
        ],
        "requestBody": {
          "required": true,
          "content": {
            "application/json": {
              "schema": {
                "type": "object",
                "required": ["model", "max_tokens", "messages"],
                "properties": {
                  "model": {
                    "type": "string",
                    "description": "Claude model identifier. Examples: claude-opus-4-7, claude-sonnet-4-6, claude-haiku-4-5-20251001.",
                    "example": "claude-sonnet-4-6"
                  },
                  "max_tokens": {
                    "type": "integer",
                    "description": "Maximum number of tokens to generate before stopping.",
                    "example": 1024
                  },
                  "messages": {
                    "type": "array",
                    "description": "Conversation turns.",
                    "items": {
                      "type": "object",
                      "required": ["role", "content"],
                      "properties": {
                        "role": {
                          "type": "string",
                          "enum": ["user", "assistant"]
                        },
                        "content": {
                          "description": "String or array of content blocks.",
                          "oneOf": [
                            { "type": "string" },
                            { "type": "array", "items": { "type": "object" } }
                          ]
                        }
                      }
                    },
                    "example": [
                      { "role": "user", "content": "Hello, Claude" }
                    ]
                  },
                  "system": {
                    "description": "System prompt. String or array of text blocks.",
                    "oneOf": [
                      { "type": "string" },
                      { "type": "array", "items": { "type": "object" } }
                    ]
                  },
                  "temperature": {
                    "type": "number",
                    "format": "float",
                    "minimum": 0.0,
                    "maximum": 1.0,
                    "default": 1.0,
                    "description": "Randomness. 0 = deterministic, 1 = creative."
                  },
                  "top_p": {
                    "type": "number",
                    "format": "float",
                    "description": "Nucleus sampling. Use instead of temperature."
                  },
                  "top_k": {
                    "type": "integer",
                    "description": "Only sample from the top K options for each token."
                  },
                  "stop_sequences": {
                    "type": "array",
                    "items": { "type": "string" },
                    "description": "Custom sequences that stop generation."
                  },
                  "stream": {
                    "type": "boolean",
                    "default": false,
                    "description": "Enable SSE streaming."
                  },
                  "tools": {
                    "type": "array",
                    "description": "Tools the model may use.",
                    "items": {
                      "type": "object",
                      "required": ["name", "input_schema"],
                      "properties": {
                        "name": { "type": "string" },
                        "description": { "type": "string" },
                        "input_schema": { "type": "object" },
                        "type": { "type": "string", "example": "custom" }
                      }
                    }
                  },
                  "tool_choice": {
                    "type": "object",
                    "description": "How the model uses tools.",
                    "properties": {
                      "type": {
                        "type": "string",
                        "enum": ["auto", "any", "tool", "none"]
                      },
                      "name": {
                        "type": "string",
                        "description": "Required when type is tool."
                      },
                      "disable_parallel_tool_use": {
                        "type": "boolean",
                        "default": false
                      }
                    }
                  },
                  "thinking": {
                    "type": "object",
                    "description": "Enable extended thinking for complex reasoning.",
                    "properties": {
                      "type": { "type": "string", "enum": ["enabled"] },
                      "budget_tokens": { "type": "integer", "example": 10000 },
                      "display": { "type": "string", "enum": ["summarized", "omitted"] }
                    }
                  },
                  "metadata": {
                    "type": "object",
                    "properties": {
                      "user_id": {
                        "type": "string",
                        "description": "External user ID (no PII)."
                      }
                    }
                  },
                  "service_tier": {
                    "type": "string",
                    "enum": ["auto", "standard_only"],
                    "default": "auto"
                  }
                }
              }
            }
          }
        },
        "responses": {
          "200": {
            "description": "Successful response",
            "content": {
              "application/json": {
                "schema": {
                  "type": "object",
                  "properties": {
                    "id": { "type": "string", "example": "msg_024e7cf42f5d47cfa6982b5ff8b55642" },
                    "type": { "type": "string", "example": "message" },
                    "role": { "type": "string", "example": "assistant" },
                    "content": {
                      "type": "array",
                      "description": "Response content blocks (text, tool_use, thinking, etc.).",
                      "items": { "type": "object" }
                    },
                    "model": { "type": "string", "example": "claude-sonnet-4-6" },
                    "stop_reason": {
                      "type": "string",
                      "enum": ["end_turn", "stop_sequence", "max_tokens", "tool_use"]
                    },
                    "stop_sequence": { "type": "string", "nullable": true },
                    "usage": {
                      "type": "object",
                      "properties": {
                        "input_tokens": { "type": "integer" },
                        "output_tokens": { "type": "integer" },
                        "cache_creation_input_tokens": { "type": "integer" },
                        "cache_read_input_tokens": { "type": "integer" }
                      }
                    }
                  }
                }
              }
            }
          },
          "400": { "description": "Invalid request parameters" },
          "401": { "description": "Missing or invalid API key" },
          "429": { "description": "Rate limit exceeded" },
          "500": { "description": "Internal server error" }
        }
      }
    }
  }
}