Slack User MCP Server

Instructions

Implementation Reference

• index.ts:441-456 (handler)

  MCP tool handler for 'slack_add_reaction': validates arguments and calls SlackClient.addReaction method.

  case "slack_add_reaction": {
    const args = request.params.arguments as unknown as AddReactionArgs;
    if (!args.channel_id || !args.timestamp || !args.reaction) {
      throw new Error(
        "Missing required arguments: channel_id, timestamp, and reaction",
      );
    }
    const response = await slackClient.addReaction(
      args.channel_id,
      args.timestamp,
      args.reaction,
    );
    return {
      content: [{ type: "text", text: JSON.stringify(response) }],
    };
  }

• index.ts:278-294 (helper)

  SlackClient method that performs the HTTP POST to Slack's reactions.add API to add the reaction.

  async addReaction(
    channel_id: string,
    timestamp: string,
    reaction: string,
  ): Promise<any> {
    const response = await fetch("https://slack.com/api/reactions.add", {
      method: "POST",
      headers: this.headers,
      body: JSON.stringify({
        channel: channel_id,
        timestamp: timestamp,
        name: reaction,
      }),
    });
  
    return response.json();
  }

• index.ts:116-137 (schema)

  Tool schema definition including name, description, and input schema for 'slack_add_reaction'.

  const addReactionTool: Tool = {
    name: "slack_add_reaction",
    description: "Add a reaction emoji to a message",
    inputSchema: {
      type: "object",
      properties: {
        channel_id: {
          type: "string",
          description: "The ID of the channel containing the message",
        },
        timestamp: {
          type: "string",
          description: "The timestamp of the message to react to",
        },
        reaction: {
          type: "string",
          description: "The name of the emoji reaction (without ::)",
        },
      },
      required: ["channel_id", "timestamp", "reaction"],
    },
  };

• index.ts:28-32 (schema)

  TypeScript interface defining the arguments for slack_add_reaction tool.

  interface AddReactionArgs {
    channel_id: string;
    timestamp: string;
    reaction: string;
  }

• index.ts:532-546 (registration)

  Registers the slack_add_reaction tool (as addReactionTool) in the list of available tools returned by ListToolsRequest.

  server.setRequestHandler(ListToolsRequestSchema, async () => {
    console.error("Received ListToolsRequest");
    return {
      tools: [
        listChannelsTool,
        postMessageTool,
        replyToThreadTool,
        addReactionTool,
        getChannelHistoryTool,
        getThreadRepliesTool,
        getUsersTool,
        getUserProfileTool,
      ],
    };
  });