{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "$schema": {
      // Explicitly allow JSON-Schema to be referenced (needed due to additionalProperties: false)
      "type": "string",
      "format": "uri"
    },
    "invocation_id": {
      "type": "string",
      "description": "ID of this specific tool call"
    },
    "duration": {
      "type": "number",
      "description": "The duration of the tool call, in milliseconds"
    },
    "finished_at": {
      "type": "string",
      "format": "date-time"
    },
    "success": {
      "type": "boolean",
      "description": "Whether the tool call was successful"
    },
    "output": {
      // Can be null/omitted, in the case of a null-returning (void) function
      "type": "object",
      "oneOf": [
        {
          "properties": {
            "value": {
              "description": "The value returned from the function",
              "oneOf": [
                { "type": "object", "additionalProperties": true }, // aka JSON
                { "type": "number" },
                { "type": "string" },
                { "type": "boolean" }
              ]
            }
          },
          "required": ["value"],
          "additionalProperties": false
        },
        {
          "properties": {
            "error": {
              "type": "object",
              "properties": {
                "message": {
                  "type": "string",
                  "description": "An error message that can be shown to the user or the AI model"
                },
                "developer_message": {
                  "type": "string",
                  "description": "An internal message that will be logged but will not be shown to the user or the AI model"
                }
              },
              "required": ["message"],
              "additionalProperties": false
            }
          },
          "required": ["error"],
          "additionalProperties": false
        },
        {
          "properties": {
            "requires_authorization": {
              "type": "object",
              "properties": {
                "message": {
                  "type": "string",
                  "description": "A message that can be shown to the user or AI model that explains the authorization requirement"
                },
                "oauth2": {
                  "type": "object",
                  "properties": {
                    "url": {
                      "type": "string",
                      "format": "uri"
                    },
                    "scope": {
                      "type": "string"
                    }
                  },
                  "required": ["url"],
                  "additionalProperties": false
                }
              },
              "required": ["message"],
              "additionalProperties": false
            }
          },
          "required": ["requires_authorization"],
          "additionalProperties": false
        },
        {
          "properties": {
            "artifact": {
              "type": "object",
              "properties": {
                "url": {
                  "type": "string",
                  "format": "uri",
                  "description": "The location of the stored artifact"
                },
                "content_type": {
                  "type": "string",
                  "description": "The MIME Media Type of the data inside the artifact (e.g. text/csv or application/json)"
                },
                "size": {
                  "type": "integer",
                  "description": "The size of the artifact, in bytes"
                },
                "meta": {
                  "type": "object",
                  "properties": {
                    "description": {
                      "type": "string",
                      "description": "A descriptive, human-readable explanation of the data inside the artifact"
                    }
                  },
                  "required": ["description"],
                  "additionalProperties": false
                }
              },
              "required": ["url", "content_type", "size", "meta"],
              "additionalProperties": false
            }
          },
          "required": ["artifact"],
          "additionalProperties": false
        }
      ]
    }
  },
  "required": ["invocation_id", "finished_at", "success"],
  "additionalProperties": false
}