> ## Documentation index > Fetch the complete documentation index at: https://dify-docs.docs7.io/llms.txt > Ask it with GET https://dify-docs.docs7.io/ask?q=. Short keywords rank best. > Use these to discover all available pages before exploring further. # 工具返回 > 工具插件如何返回消息（文本、链接、图片、文件、JSON）、创建标准变量和流式变量，以及定义输出模式以供工作流引用 > 本文档由 AI 自动翻译。如有任何不准确之处，请参考 [英文原版](/en/develop-plugin/features-and-specs/plugin-types/tool)。 ## 概述工具以消息和变量的形式返回结果。本页介绍消息接口、变量创建和输出模式定义。返回不同类型的消息，如文本、链接、图片和 JSON 创建和操作变量以实现工作流集成定义自定义输出变量以供工作流引用 ## 数据结构 ### 消息返回 Dify 支持多种消息类型，包括文本、链接、图片、文件 blob 和 JSON，每种类型都通过专用接口返回。默认情况下，工作流中工具的输出包含三个固定变量：`files`、`text` 和 `json`。以下方法用于填充这些变量。虽然你可使用 `create_image_message` 等方法返回图片，但工具也支持自定义输出变量，从而更便于在工作流中引用特定数据。 ### 消息类型 ```python Image URL def create_image_message(self, image: str) -> ToolInvokeMessage: """ Return an image URL message Dify will automatically download the image from the provided URL and display it to the user. Args: image: URL to an image file Returns: ToolInvokeMessage: Message object for the tool response """ pass ``` ```python Link def create_link_message(self, link: str) -> ToolInvokeMessage: """ Return a clickable link message Args: link: URL to be displayed as a clickable link Returns: ToolInvokeMessage: Message object for the tool response """ pass ``` ```python Text def create_text_message(self, text: str) -> ToolInvokeMessage: """ Return a text message Args: text: Text content to be displayed Returns: ToolInvokeMessage: Message object for the tool response """ pass ``` ```python File def create_blob_message(self, blob: bytes, meta: dict = None) -> ToolInvokeMessage: """ Return a file blob message For returning raw file data such as images, audio, video, or documents (PPT, Word, Excel, etc.) Args: blob: Raw file data in bytes meta: File metadata dictionary. Include 'mime_type' to specify the file type, otherwise 'octet/stream' will be used Returns: ToolInvokeMessage: Message object for the tool response """ pass ``` ```python JSON def create_json_message(self, json: dict) -> ToolInvokeMessage: """ Return a formatted JSON message Useful for data transmission between workflow nodes. In agent mode, most LLMs can read and understand JSON data. Args: json: Python dictionary to be serialized as JSON Returns: ToolInvokeMessage: Message object for the tool response """ pass ``` 将被下载并显示的图片 URL 将显示为可点击链接的 URL 要显示的文本内容字节格式的原始文件数据文件元数据，包括： - `mime_type`：文件的 MIME 类型（例如 `image/png`） - 与文件相关的其他元数据要序列化为 JSON 的 Python 字典处理文件 blob 时，请始终在 `meta` 字典中指定 `mime_type`，以确保文件得到正确处理。例如：`{"mime_type": "image/png"}`。 ### 变量 ```python Standard Variable from typing import Any def create_variable_message(self, variable_name: str, variable_value: Any) -> ToolInvokeMessage: """ Create a named variable for workflow integration For non-streaming output variables. If multiple instances with the same name are created, the latest one overrides previous values. Args: variable_name: Name of the variable to create variable_value: Value of the variable (any Python data type) Returns: ToolInvokeMessage: Message object for the tool response """ pass ``` ```python Streaming Variable def create_stream_variable_message( self, variable_name: str, variable_value: str ) -> ToolInvokeMessage: """ Create a streaming variable with typewriter effect When referenced in an answer node in a chatflow application, the text will be output with a typewriter effect. Args: variable_name: Name of the variable to create variable_value: String value to stream (only strings supported) Returns: ToolInvokeMessage: Message object for the tool response """ pass ``` 要创建或更新的变量名称要分配给变量的值： - 标准变量：任何 Python 数据类型 - 流式变量：仅支持字符串数据 `create_stream_variable_message` 目前仅支持字符串数据。复杂数据类型无法通过打字机效果进行流式输出。 ## 自定义输出变量要在 Workflow 应用中引用工具的输出变量，需在工具清单中使用 [JSON Schema](https://json-schema.org/) 声明工具可能输出的变量。 ### 定义输出模式 ```yaml Tool Manifest with Output Schema identity: author: example_author name: example_tool label: en_US: Example Tool zh_Hans: 示例工具 ja_JP: ツール例 pt_BR: Ferramenta de exemplo description: human: en_US: A simple tool that returns a name zh_Hans: 返回名称的简单工具 ja_JP: 名前を返す簡単なツール pt_BR: Uma ferramenta simples que retorna um nome llm: A simple tool that returns a name variable output_schema: type: object properties: name: type: string description: "The name returned by the tool" age: type: integer description: "The age returned by the tool" profile: type: object properties: interests: type: array items: type: string location: type: string ``` 定义工具输出模式的根对象工具输出模式必须为 `object` 所有可能输出变量的字典每个输出变量的定义，包括其类型和描述仅定义输出模式还不够：实现代码仍须使用 `create_variable_message()` 返回每个变量。否则，工作流将收到该变量的 `None` 值。 ### 实现示例 ```python Basic Variable Example def run(self, inputs): # Process inputs and generate a name generated_name = "Alice" # Return the name as a variable that matches the output_schema return self.create_variable_message("name", generated_name) ``` ```python Complex Structure Example def run(self, inputs): # Generate complex structured data user_data = { "name": "Bob", "age": 30, "profile": { "interests": ["coding", "reading", "hiking"], "location": "San Francisco" } } # Return individual variables self.create_variable_message("name", user_data["name"]) self.create_variable_message("age", user_data["age"]) self.create_variable_message("profile", user_data["profile"]) # Also return a text message for display return self.create_text_message(f"User {user_data['name']} processed successfully") ``` 对于复杂的工作流，您可以定义多个输出变量并全部返回。这为工作流设计者使用您的工具时提供了更大的灵活性。 ## 示例 ### 完整的工具实现 ```python Weather Forecast Tool import requests from typing import Any class WeatherForecastTool: def run(self, inputs: dict) -> Any: # Get location from inputs location = inputs.get("location", "London") try: # Call weather API (example only) weather_data = self._get_weather_data(location) # Create variables for workflow use self.create_variable_message("temperature", weather_data["temperature"]) self.create_variable_message("conditions", weather_data["conditions"]) self.create_variable_message("forecast", weather_data["forecast"]) # Create a JSON message for data transmission self.create_json_message(weather_data) # Create an image message for the weather map self.create_image_message(weather_data["map_url"]) # Return a formatted text response return self.create_text_message( f"Weather in {location}: {weather_data['temperature']}°C, {weather_data['conditions']}. " f"Forecast: {weather_data['forecast']}" ) except Exception as e: # Handle errors gracefully return self.create_text_message(f"Error retrieving weather data: {str(e)}") def _get_weather_data(self, location: str) -> dict: # Mock implementation - in a real tool, this would call a weather API return { "location": location, "temperature": 22, "conditions": "Partly Cloudy", "forecast": "Sunny with occasional showers tomorrow", "map_url": "https://example.com/weather-map.png" } ``` 设计工具时，请同时考虑直接输出（用户看到的内容）和变量输出（其他工作流节点可以使用的内容）。这种分离为工具的使用方式提供了灵活性。