People use Slack to communicate, collaborate, and get work done. A great Slack app follows this pattern and goes a step further by building on Slack’s platform of trust and reliability. For Marketplace apps, that means getting permissions, messaging, interactions, and infrastructure right across every workspace where your app is installed.

Whether you’re building a new app or converting an existing one, these tips will help set your app up for success.

Design messages that belong in Slack

A Slack app communicates through its messages. Well-designed messages reduce noise and help users stay focused. Structuring your content clearly is a big part of that. 

Slack’s UI framework, Block Kit, makes this easy. Block Kit lets you build rich messages with layouts, buttons, menus, and interactive components. This framework also works across messages, modals, and the App Home tab. Everything you build with it renders consistently across desktop, mobile, and notifications. You can prototype and preview layouts visually with Block Kit Builder before writing any code.

Be careful with notifications. Let users configure notification type and frequency for their workspace. Batch high-volume notifications or create digests instead of firing them one by one. Only use @channel or @everyone when the situation genuinely warrants it (nearly never, per Slack’s best practices), and never default-post to #general.

Don’t send notifications to people who wouldn’t expect to receive them. When configuring notifications for a shared channel, post an intro message attributing the setup to the person who configured it. Use the App Home Messages tab for app-to-user notifications.

Finally, make sure your messages are accessible. Either include all necessary content in the top-level text field, or omit it and let Slack build it by appending content from supported blocks. Screen readers default to the top-level text field and won’t read interior blocks. Whichever approach you choose, verify the result is readable.

Build interactions that chain naturally

People collaborate in Slack by moving through conversations, decisions, and actions. The best Slack apps support that flow by chaining interactions together. This keeps users in context without forcing them to leave Slack.

Every interaction follows a simple pattern. First, a trigger happens via a shortcut, slash command, scheduled event,  button click, etc. Then your app responds by sending a message, opening a modal, updating the Home tab, or other action. Chaining these together keeps complex workflows contained within Slack’s familiar interface.

Choose the right trigger for each interaction. Shortcuts work well for quick, frequent actions. Slash commands are suited for power-user operations that benefit from typed input. Use Block Kit components for in-context actions within messages. For automated workflows that fire without user action, use scheduled events and webhooks.

Invest in onboarding

Your app should help people get work done from the moment they install it. A user who doesn’t understand your app quickly is unlikely to keep it installed.

Show users what your app does within the first interaction, with clear visual feedback and guidance at every step. Design these flows to scale across hundreds of workspaces without manual intervention. Your App Home tab is the most customizable surface you have, and it’s a natural place for onboarding, instructions, and persistent context.

Not every user will arrive ready to go. If your app requires a third-party account, support the case where a user installs without one. Guide them to create or connect an account rather than leaving them stuck. Make sure they can reach your support resources without needing to create an account first.

Design a quality user experience

Reliability is consistency. Users should know what to expect when they click around in your app. If something goes wrong, they should be able to pick up where they left off.

Provide clear feedback on user actions: buttons should appear clicked, submissions confirmed, and loading states shown. Write error messages that tell users what to do next. Let users go back from any action. Give every screen a clear next step. In shared spaces, attribute app actions so other channel members aren’t confused about who triggered them.

When you build with these patterns, your app becomes part of how people already communicate and collaborate. From there, your app becomes part of how people work, not something they work around. Ready to go deeper? The next post in this series covers earning and keeping trust through permissions, security, and reliability.