Slack MCP Server

Instructions

Implementation Reference

• src/tools.ts:134-179 (handler)

  The core handler function for the 'conversations_history' tool. Validates input using Zod schema, resolves channel IDs, parses limits, calls Slack's conversations.history API, filters messages, and handles errors.
  /** * Tool: conversations_history * Retrieves message history from a Slack channel, DM, or thread */ export async function conversationsHistory(args: any): Promise<ToolResponse> { try { const validated = ConversationsHistorySchema.parse(args); const client = new WebClient(validated.accessToken); console.log('Fetching conversation history for channel:', validated.channel_id); // Resolve channel name/username to ID if needed const channelId = await resolveChannelId(client, validated.channel_id); // Parse limit parameter const limitParams = parseLimit(validated.limit); // Fetch conversation history const result = await client.conversations.history({ channel: channelId, cursor: validated.cursor, ...limitParams }); // Filter out activity messages if not requested let messages = result.messages || []; if (!validated.include_activity_messages) { messages = messages.filter((msg: any) => !msg.subtype || !['channel_join', 'channel_leave'].includes(msg.subtype)); } return { success: true, data: { messages, has_more: result.has_more, cursor: result.response_metadata?.next_cursor, channel_id: channelId } }; } catch (error: any) { if (error.name === 'ZodError') { return { success: false, error: `Validation error: ${error.errors.map((e: any) => e.message).join(', ')}` }; } return handleSlackError(error); } }
• src/schemas.ts:4-13 (schema)

  Zod input schema definition for the conversations_history tool, defining parameters like accessToken, channel_id, limit, cursor, and include_activity_messages.
  * Schema for conversations_history tool * Retrieves message history from a Slack channel, DM, or thread */ export const ConversationsHistorySchema = z.object({ accessToken: z.string().describe("Slack OAuth token (xoxp-... or xoxb-...)"), channel_id: z.string().describe("Channel ID (e.g., C1234567890), channel name (#general), or DM (@username)"), limit: z.union([z.string(), z.number()]).optional().describe("Time range (1d, 7d, 1m, 90d) or message count (e.g., 100)"), cursor: z.string().optional().describe("Pagination cursor from previous response"), include_activity_messages: z.boolean().optional().describe("Include join/leave system messages (default: false)") });
• src/index.ts:96-100 (registration)

  Registration of the conversations_history tool in the MCP server's listTools handler, specifying name, description, and converting Zod schema to MCP inputSchema.
  name: 'conversations_history', description: 'Retrieves message history from a Slack channel, DM, or thread. Supports pagination and filtering.', inputSchema: zodToMCPSchema(ConversationsHistorySchema) }, {
• src/index.ts:129-131 (registration)

  Registration of the conversations_history tool execution in the MCP server's callTool handler switch statement.
  case 'conversations_history': result = await conversationsHistory(args); break;
• src/tools.ts:64-95 (helper)

  Helper utility function used by conversations_history to resolve channel names (#channel) or usernames (@user) to actual Slack channel IDs.
  async function resolveChannelId(client: WebClient, channelInput: string): Promise<string> { // If already an ID (starts with C, D, or G), return as-is if (/^[CDG][A-Z0-9]+$/.test(channelInput)) { return channelInput; } // Handle #channel format if (channelInput.startsWith('#')) { const channelName = channelInput.slice(1); const result = await client.conversations.list({ types: 'public_channel,private_channel' }); const channel = result.channels?.find((ch: any) => ch.name === channelName); if (channel) { return channel.id!; } throw new Error(`Channel not found: ${channelInput}`); } // Handle @username format for DMs if (channelInput.startsWith('@')) { const username = channelInput.slice(1); const usersResult = await client.users.list({}); const user = usersResult.members?.find((u: any) => u.name === username); if (user) { // Open or get existing DM const dmResult = await client.conversations.open({ users: user.id! }); return dmResult.channel!.id!; } throw new Error(`User not found: ${channelInput}`); } return channelInput; // Return as-is if no special format }