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MCP APPS

Some steps need a screen, not a sentence.

A chat window is a rectangle for words. Plenty of real work is not words — it is a file, a date, a total somebody signs off. An MCP App is a tool that brings its own interface and opens it right there in the thread.

WHERE TEXT RUNS OUT
  • A file has to go upNobody pastes a PDF into a chat message. An upload needs a control.
  • A date has to be picked“Next Tuesday” is three different days depending on who is reading.
  • A total has to be checkedBefore money moves, somebody wants to see the number and press the button themselves.
  • One of 300 rows has to be chosenA list that long is unreadable as text and trivial as a picker.
ONE RUNNING

This is the whole idea.

You ask. The assistant calls one tool. The tool's own screen opens inside the conversation, you check it and press the button, and four systems do their part in order.

Gmail Notion Drive Asana one app
CONNECTED TO INLINE
Set up Northwind as a new client — standard plan, Maya owns it.

You have an app for that. Here it is — check the details and run it.

new_client_onboarding running
INLINE APP New client onboarding
CLIENT Northwind Ltd
OWNER maya@yourcompany.com
PLAN Standard — monthly
SET THEM UP
  1. 01 Drive created the client folder
  2. 02 Notion added their page to the CRM
  3. 03 Gmail sent the welcome email
  4. 04 Asana started the onboarding checklist

Northwind is set up. Folder, CRM page, welcome email and checklist — all four, in that order.

The tool works in any MCP client. The screen appears wherever the host supports MCP Apps — everywhere else the same tool runs and asks for what it needs in words.

WHAT IT ACTUALLY IS

Not our invention — but it used to take a front-end project.

MCP Apps is a published extension to the Model Context Protocol. A tool can declare an HTML resource, and a host that supports it renders that HTML in a sandboxed frame inside the conversation, talking back to the server over the same connection. The standard is open. What was missing was a way to get one without building it.

  • Inline generates the screen from the tool you already made
  • Fields come from the tool's own arguments
  • It runs against your connected accounts, not a copy of your data
  • Hosts that do not support apps still get a working plain tool
tool     new_client_onboarding
ui       ui://inline/new-client-onboarding

  renders   inside the conversation
  sandbox   iframe, no page access
  talks     JSON-RPC, same connection

  fallback  plain tool call, no screen
THE HONEST PART

Support is still arriving.

MCP Apps is new, and not every host renders one yet. A tool built here works either way: where apps are supported you get the screen, and where they are not the assistant calls the same tool and asks for the missing pieces in words. You do not build it twice, and you do not have to wait.

Build one free See the whole flow