Slack MCP Server

Instructions

Implementation Reference

• src/tools/messages.ts:11-28 (handler)

  The main handler function for the 'send_message' tool. It validates input using sendMessageSchema, calls Slack's chat.postMessage API, and returns the result.

  export async function sendMessage(client: SlackClientWrapper, args: unknown) {
    const params = sendMessageSchema.parse(args);
  
    return await client.safeCall(async () => {
      const result = await client.getClient().chat.postMessage({
        channel: params.channel,
        text: params.text,
        thread_ts: params.thread_ts,
      });
  
      return {
        ok: true,
        channel: result.channel,
        ts: result.ts,
        message: result.message,
      };
    });
  }

• src/utils/validators.ts:47-51 (schema)

  Zod schema used for input validation in the send_message handler.

  export const sendMessageSchema = z.object({
    channel: channelIdSchema,
    text: z.string().min(1),
    thread_ts: timestampSchema.optional(),
  });

• src/index.ts:173-194 (registration)

  Tool definition for 'send_message' in the tools array returned by list_tools, including input schema.

  {
    name: 'send_message',
    description: 'Send a message to a channel',
    inputSchema: {
      type: 'object',
      properties: {
        channel: {
          type: 'string',
          description: 'Channel ID',
        },
        text: {
          type: 'string',
          description: 'Message text',
        },
        thread_ts: {
          type: 'string',
          description: 'Optional thread timestamp to reply to',
        },
      },
      required: ['channel', 'text'],
    },
  },

• src/index.ts:426-426 (registration)

  Handler registration mapping 'send_message' calls to messageTools.sendMessage in the toolHandlers object for call_tool requests.

  send_message: (args) => messageTools.sendMessage(slackClient, args),