Slackbot · MCP testing
Test your MCP app's UI in Slackbot.
Slackbot renders MCP apps in inline and fullscreen mode, inside a frame up to 598px wide. Your app has to look right in that envelope. MCPJam renders it locally against Slackbot's real context so you see it before your users do.
npx @mcpjam/inspector@latestSlackbot's app envelope
Display modes
Slackbot supports inline and fullscreen, defaulting to inline. Your app has to hold up in each one.
Viewport
Apps render in a frame up to 598px wide on web. Design and test to that box, not to your dev browser.
Media placement
No tool-result media placement in Slackbot. Media returned by tools won't render in the app surface.
Theme
Slackbot's context reports a dark theme, pointer input (no touch). Test your app's contrast there.
Local, no tunnel
MCPJam's App Builder emulates the app locally and previews across viewports, with no ChatGPT subscription and a built-in tunnel when you need to test in a real client.
How we know
Probed: Verified by running against the client. Last reviewed 2026-07-08.
Walkthrough: Slackbot
- Run npx @mcpjam/inspector@latest.
- Connect the MCP server config you already use.
- Select Slackbot as the host. MCPJam emulates Slackbot with openai/gpt-5-nano on web, so what you see is this host's behavior, not a generic client's.
- Open your app in the App Builder preview. It renders in Slackbot's frame (up to 598px wide), in inline and fullscreen mode, with no subscription needed and a built-in tunnel when you need to test in a real client.
- Resize across the previews and confirm nothing clips.
Frequently asked questions
Run npx @mcpjam/inspector@latest, connect your server, and select Slackbot. MCPJam emulates the host with openai/gpt-5-nano, so you can watch the real behavior locally, free and open source.
Slackbot renders apps in a frame up to 598px wide, supporting inline and fullscreen display modes. (Catalog last reviewed 2026-07-08.)
MCPJam's host-compat catalog (the same data behind caniuse.dev). Probed: Verified by running against the client. Last reviewed 2026-07-08.
See it in Slackbot before your users do.
One command, your existing server config, Slackbot's real behavior in the loop.
Open source · no credit card · ~2 min