Slack MCP Server

Instructions

Implementation Reference

• src/index.ts:237-250 (handler)

  The main handler function for the 'slack_add_reaction' tool. Parses input using AddReactionRequestSchema, calls slackClient.reactions.add with channel_id, timestamp, and reaction, and returns success message.

  case 'slack_add_reaction': {
    const args = AddReactionRequestSchema.parse(request.params.arguments);
    const response = await slackClient.reactions.add({
      channel: args.channel_id,
      timestamp: args.timestamp,
      name: args.reaction,
    });
    if (!response.ok) {
      throw new Error(`Failed to add reaction: ${response.error}`);
    }
    return {
      content: [{ type: 'text', text: 'Reaction added successfully' }],
    };
  }

• src/schemas.ts:101-114 (schema)

  Zod input schema definition for the slack_add_reaction tool, validating channel_id, reaction emoji name, and message timestamp.

  export const AddReactionRequestSchema = z.object({
    channel_id: z
      .string()
      .describe('The ID of the channel containing the message'),
    reaction: z.string().describe('The name of the emoji reaction (without ::)'),
    timestamp: z
      .string()
      .regex(/^\d{10}\.\d{6}$/, {
        message: "Timestamp must be in the format '1234567890.123456'",
      })
      .describe(
        "The timestamp of the message to react to in the format '1234567890.123456'"
      ),
  });

• src/index.ts:131-135 (registration)

  Tool registration in the listTools handler, defining name, description, and inputSchema for slack_add_reaction.

  {
    name: 'slack_add_reaction',
    description: 'Add a reaction emoji to a message',
    inputSchema: zodToJsonSchema(AddReactionRequestSchema),
  },