slack_add_reaction

Add emoji reactions to Slack messages to acknowledge, respond, or categorize content in channels using channel ID, message timestamp, and emoji name.

Instructions

Add a reaction emoji to a message

Input Schema

TableJSON Schema

Name	Required	Description
`channel_id`	Yes	The ID of the channel containing the message
`timestamp`	Yes	The timestamp of the message to react to
`reaction`	Yes	The name of the emoji reaction (without ::)

Implementation Reference

index.ts:296-301 (handler)

MCP tool handler for slack_add_reaction that invokes the SlackClient addReaction method and formats the response as MCP content.

async ({ channel_id, timestamp, reaction }) => {
  const response = await slackClient.addReaction(channel_id, timestamp, reaction);
  return {
    content: [{ type: "text", text: JSON.stringify(response) }],
  };
}

index.ts:290-294 (schema)

Zod input schema defining parameters for the slack_add_reaction tool.

inputSchema: {
  channel_id: z.string().describe("The ID of the channel containing the message"),
  timestamp: z.string().describe("The timestamp of the message to react to"),
  reaction: z.string().describe("The name of the emoji reaction (without ::)"),
},

index.ts:285-302 (registration)

Registration of the slack_add_reaction tool with schema and handler on the MCP server.

server.registerTool(
  "slack_add_reaction",
  {
    title: "Add Slack Reaction",
    description: "Add a reaction emoji to a message",
    inputSchema: {
      channel_id: z.string().describe("The ID of the channel containing the message"),
      timestamp: z.string().describe("The timestamp of the message to react to"),
      reaction: z.string().describe("The name of the emoji reaction (without ::)"),
    },
  },
  async ({ channel_id, timestamp, reaction }) => {
    const response = await slackClient.addReaction(channel_id, timestamp, reaction);
    return {
      content: [{ type: "text", text: JSON.stringify(response) }],
    };
  }
);

index.ts:142-158 (helper)

SlackClient.addReaction helper method implementing the Slack API call to add a reaction to a message.

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.botHeaders,
    body: JSON.stringify({
      channel: channel_id,
      timestamp: timestamp,
      name: reaction,
    }),
  });

  return response.json();
}

index.ts:28-32 (schema)
TypeScript interface defining the argument types for the addReaction method.
```
interface AddReactionArgs {
  channel_id: string;
  timestamp: string;
  reaction: string;
}
```

Slack