Slack MCP Server

Instructions

Implementation Reference

• src/index.ts:271-289 (handler)

  The handler function for slack_get_thread_replies that parses input arguments, calls slackClient.conversations.replies API, validates response with schema, and returns JSON stringified result.

  case 'slack_get_thread_replies': {
    const args = GetThreadRepliesRequestSchema.parse(
      request.params.arguments
    );
    const response = await slackClient.conversations.replies({
      channel: args.channel_id,
      ts: args.thread_ts,
      limit: args.limit,
      cursor: args.cursor,
    });
    if (!response.ok) {
      throw new Error(`Failed to get thread replies: ${response.error}`);
    }
    const parsedResponse =
      ConversationsRepliesResponseSchema.parse(response);
    return {
      content: [{ type: 'text', text: JSON.stringify(parsedResponse) }],
    };
  }

• src/schemas.ts:136-160 (schema)

  Input schema (Zod) for the tool defining parameters: channel_id, thread_ts (validated timestamp format), optional cursor and limit.

  export const GetThreadRepliesRequestSchema = z.object({
    channel_id: z
      .string()
      .describe('The ID of the channel containing the thread'),
    thread_ts: z
      .string()
      .regex(/^\d{10}\.\d{6}$/, {
        message: "Timestamp must be in the format '1234567890.123456'",
      })
      .describe(
        "The timestamp of the parent message in the format '1234567890.123456'. Timestamps in the format without the period can be converted by adding the period such that 6 numbers come after it."
      ),
    cursor: z
      .string()
      .optional()
      .describe('Pagination cursor for next page of results'),
    limit: z
      .number()
      .int()
      .min(1)
      .max(1000)
      .optional()
      .default(100)
      .describe('Number of replies to retrieve (default 100)'),
  });

• src/index.ts:142-146 (registration)

  Registration of the tool in the ListToolsRequestHandler, specifying name, description, and inputSchema.

  {
    name: 'slack_get_thread_replies',
    description: 'Get all replies in a message thread',
    inputSchema: zodToJsonSchema(GetThreadRepliesRequestSchema),
  },

• src/schemas.ts:394-396 (schema)

  Response schema used to parse the Slack API conversations.replies response.

  export const ConversationsRepliesResponseSchema = BaseResponseSchema.extend({
    messages: z.array(ConversationsHistoryMessageSchema).optional(),
  });