Slack Expert Skill

Overview

Full-platform Slack development using the Bolt SDK. Covers interactive app development beyond basic messaging — slash commands, modals, shortcuts, home tabs, event subscriptions, workflow steps, and multi-workspace OAuth.

Related skill: slack-notifications — use that skill for simple one-way messaging/alerts. Use slack-expert when building interactive Slack apps or bots.

Requirements

Quick Start — Bolt App (Node.js)

const { App } = require('@slack/bolt');

const app = new App({
  token: process.env.SLACK_BOT_TOKEN,
  signingSecret: process.env.SLACK_SIGNING_SECRET,
  // For Socket Mode, add:
  socketMode: true,
  appToken: process.env.SLACK_APP_TOKEN,
});

// Slash command
app.command('/hello', async ({ command, ack, respond }) => {
  await ack();
  await respond(`Hello <@${command.user_id}>!`);
});

// Button click
app.action('approve_button', async ({ body, ack, client }) => {
  await ack();
  await client.views.open({
    trigger_id: body.trigger_id,
    view: confirmationModal,
  });
});

// Event subscription
app.event('app_mention', async ({ event, say }) => {
  await say({ text: `Hello <@${event.user}>!`, thread_ts: event.ts });
});

(async () => {
  await app.start(process.env.PORT || 3000);
  console.log('Bolt app running');
})();

Core Concepts

Listeners

// Message listener with regex
app.message(/deploy/, async ({ message, say }) => {
  await say('Triggering deployment...');
});

// Slash command — MUST ack() within 3 seconds
app.command('/status', async ({ ack, respond, command }) => {
  await ack();
  // Long-running: defer actual work
  respond({ text: 'Checking status...', response_type: 'ephemeral' });
  const status = await fetchStatus(); // async work after ack
  await respond({ text: `Status: ${status}` });
});

// Shortcut (global or message)
app.shortcut('create_ticket', async ({ shortcut, ack, client }) => {
  await ack();
  await client.views.open({
    trigger_id: shortcut.trigger_id,
    view: ticketModal,
  });
});

Modals (Views)

const modal = {
  type: 'modal',
  callback_id: 'ticket_submission',
  title: { type: 'plain_text', text: 'Create Ticket' },
  submit: { type: 'plain_text', text: 'Submit' },
  close: { type: 'plain_text', text: 'Cancel' },
  blocks: [
    {
      type: 'input',
      block_id: 'title_block',
      element: {
        type: 'plain_text_input',
        action_id: 'title_input',
        placeholder: { type: 'plain_text', text: 'Ticket title' },
      },
      label: { type: 'plain_text', text: 'Title' },
    },
    {
      type: 'input',
      block_id: 'priority_block',
      element: {
        type: 'static_select',
        action_id: 'priority_select',
        options: [
          { text: { type: 'plain_text', text: 'High' }, value: 'high' },
          { text: { type: 'plain_text', text: 'Medium' }, value: 'medium' },
          { text: { type: 'plain_text', text: 'Low' }, value: 'low' },
        ],
      },
      label: { type: 'plain_text', text: 'Priority' },
    },
  ],
};

// Handle modal submission
app.view('ticket_submission', async ({ ack, view, client, body }) => {
  await ack();
  const title = view.state.values.title_block.title_input.value;
  const priority = view.state.values.priority_block.priority_select.selected_option.value;
  await createTicket({ title, priority, userId: body.user.id });
});

Block Kit — Rich Messages

const richMessage = {
  blocks: [
    {
      type: 'header',
      text: { type: 'plain_text', text: 'Deployment Ready' },
    },
    {
      type: 'section',
      fields: [
        { type: 'mrkdwn', text: '*Service:*\napi-gateway' },
        { type: 'mrkdwn', text: '*Version:*\nv1.2.3' },
        { type: 'mrkdwn', text: '*Environment:*\nProduction' },
        { type: 'mrkdwn', text: '*Requested by:*\n<@U1234567>' },
      ],
    },
    { type: 'divider' },
    {
      type: 'actions',
      block_id: 'deploy_actions',
      elements: [
        {
          type: 'button',
          text: { type: 'plain_text', text: 'Approve' },
          style: 'primary',
          action_id: 'approve_deploy',
          value: 'v1.2.3',
          confirm: {
            title: { type: 'plain_text', text: 'Confirm Deploy' },
            text: { type: 'mrkdwn', text: 'Deploy *v1.2.3* to production?' },
            confirm: { type: 'plain_text', text: 'Deploy' },
            deny: { type: 'plain_text', text: 'Cancel' },
          },
        },
        {
          type: 'button',
          text: { type: 'plain_text', text: 'Reject' },
          style: 'danger',
          action_id: 'reject_deploy',
          value: 'v1.2.3',
        },
      ],
    },
  ],
};

App Home Tab

// Publish home tab when user opens it
app.event('app_home_opened', async ({ event, client }) => {
  if (event.tab !== 'home') return;

  await client.views.publish({
    user_id: event.user,
    view: {
      type: 'home',
      blocks: [
        {
          type: 'header',
          text: { type: 'plain_text', text: 'My App Dashboard' },
        },
        {
          type: 'section',
          text: { type: 'mrkdwn', text: 'Welcome to your app home!' },
          accessory: {
            type: 'button',
            text: { type: 'plain_text', text: 'Refresh' },
            action_id: 'refresh_home',
          },
        },
      ],
    },
  });
});

Lazy Listeners (Long-Running Operations)

// Use lazy: for operations that take >3s
app.command(
  '/report',
  async ({ command, ack, respond, say }) => {
    await ack(); // Must ack in <3s
  },
  async ({ command, respond }) => {
    // lazy: runs asynchronously, can take minutes
    const report = await generateReport(command.text);
    await respond({ text: report, response_type: 'in_channel' });
  }
);

Socket Mode (Internal Tools)

// Socket Mode — no public URL required, ideal for internal tools
const app = new App({
  token: process.env.SLACK_BOT_TOKEN,
  signingSecret: process.env.SLACK_SIGNING_SECRET,
  socketMode: true,
  appToken: process.env.SLACK_APP_TOKEN, // xapp- token
});

OAuth (Multi-Workspace Apps)

const { App, ExpressReceiver } = require('@slack/bolt');
const { FileInstallationStore } = require('@slack/oauth');

const receiver = new ExpressReceiver({
  signingSecret: process.env.SLACK_SIGNING_SECRET,
  clientId: process.env.SLACK_CLIENT_ID,
  clientSecret: process.env.SLACK_CLIENT_SECRET,
  stateSecret: process.env.SLACK_STATE_SECRET,
  scopes: ['chat:write', 'channels:read', 'commands'],
  installationStore: new FileInstallationStore(),
});

const app = new App({ receiver });

Workflow Steps (Deprecated → Automations)

// Legacy workflow steps (still used in some workspaces)
const ws = new WorkflowStep('copy_review', {
  edit: async ({ ack, step, configure }) => {
    await ack();
    await configure({ blocks: editBlocks });
  },
  save: async ({ ack, step, view, update }) => {
    await ack();
    const { values } = view.state;
    await update({ inputs: {}, outputs: [] });
  },
  execute: async ({ step, complete, fail }) => {
    try {
      // do work
      await complete({ outputs: {} });
    } catch (err) {
      await fail({ error: { message: err.message } });
    }
  },
});
app.step(ws);

Scopes Reference

Common Patterns

Approval Workflow

app.command('/approve-request', async ({ command, ack, client }) => {
  await ack();
  // Post approval request to manager channel
  await client.chat.postMessage({
    channel: '#approvals',
    text: `<@${command.user_id}> requests approval`,
    blocks: buildApprovalBlocks(command),
  });
});

app.action('approve_action', async ({ action, body, ack, client }) => {
  await ack();
  const requestId = action.value;
  await markApproved(requestId, body.user.id);
  // Update original message
  await client.chat.update({
    channel: body.channel.id,
    ts: body.message.ts,
    text: `Approved by <@${body.user.id}>`,
    blocks: buildApprovedBlocks(requestId),
  });
});

User Lookup

async function lookupUser(client, email) {
  const result = await client.users.lookupByEmail({ email });
  return result.user.id;
}

Error Handling

app.error(async error => {
  console.error('Global error handler', error);
  // Notify admin channel
  await app.client.chat.postMessage({
    channel: process.env.ADMIN_CHANNEL,
    text: `App error: ${error.message}`,
  });
});

Security

• Always verify SLACKSIGNINGSECRET to authenticate requests from Slack
• Never log raw payloads (may contain user PII)
• Use response_type: 'ephemeral' for sensitive command responses
• Store tokens in encrypted secrets manager, not .env in production
• Scope bot tokens to minimum required permissions
• Rotate signing secrets if compromised — requires reinstalling the app

Debugging

# Enable Bolt debug logging
DEBUG=bolt:* node app.js

# Test with Slack CLI (requires Slack CLI installed)
slack run
slack triggers create --trigger-def "triggers/trigger.json"

# Replay events locally
slack events replay

Related

• slack-notifications skill — Simple one-way messaging and alerts
• Bolt JS docs: <https://slack.dev/bolt-js/>;
• Block Kit Builder: <https://app.slack.com/block-kit-builder>;
• Slack API reference: <https://api.slack.com/methods>;