Slack MCP Server

Instructions

Implementation Reference

• src/tools/reactions.ts:4-21 (handler)

  The core handler function that parses arguments using the schema, calls Slack's reactions.add API via the client wrapper, and returns a success response.

  export async function addReaction(client: SlackClientWrapper, args: unknown) {
    const params = addReactionSchema.parse(args);
  
    return await client.safeCall(async () => {
      await client.getClient().reactions.add({
        channel: params.channel,
        timestamp: params.timestamp,
        name: params.name,
      });
  
      return {
        ok: true,
        channel: params.channel,
        timestamp: params.timestamp,
        reaction: params.name,
      };
    });
  }

• src/utils/validators.ts:95-99 (schema)

  Zod schema defining the input parameters for the add_reaction tool: channel ID, message timestamp, and emoji name.

  export const addReactionSchema = z.object({
    channel: channelIdSchema,
    timestamp: timestampSchema,
    name: emojiSchema,
  });

• src/index.ts:352-373 (registration)

  Tool specification registered for the list_tools endpoint, including name, description, and JSON schema matching the Zod schema.

  {
    name: 'add_reaction',
    description: 'Add an emoji reaction to a message',
    inputSchema: {
      type: 'object',
      properties: {
        channel: {
          type: 'string',
          description: 'Channel ID',
        },
        timestamp: {
          type: 'string',
          description: 'Message timestamp',
        },
        name: {
          type: 'string',
          description: 'Emoji name (without colons)',
        },
      },
      required: ['channel', 'timestamp', 'name'],
    },
  },

• src/index.ts:437-437 (registration)

  Handler mapping in the toolHandlers object that wires the 'add_reaction' tool name to the imported addReaction function.

  add_reaction: (args) => reactionTools.addReaction(slackClient, args),