Most people who find Sidekick arrive looking for Claude. Fair enough: that is where it started, and Claude Desktop is still the one-click install. But Sidekick talks MCP, and so does the ChatGPT desktop app. This is what that looks like:
The window on the left is the ChatGPT app, the window on the right is InDesign, and nothing sits between them but Sidekick. The brief was a cookbook designer’s: a recipe spread, 210 by 260 mm, choose your own margins and grid, generate the photos, Minion Pro and Myriad Pro, make it look tasty. No template, no sketch, no existing document. One take; the stretches where ChatGPT is thinking are sped up and say so on screen.
The setup takes a few more steps than Claude’s, and two of them are easy to miss. Here they are.
Setting it up
You need three things: the InDesign plugin, Sidekick on your computer, and ChatGPT told where to find it.
1. Install the InDesign plugin
Get Sidekick from Adobe Exchange. It installs into InDesign through Creative Cloud. One subscription covers every assistant on your computer.
2. Install Sidekick on your computer
ChatGPT has no extension format, so Sidekick runs as a small program that ChatGPT starts when it needs it. The ChatGPT install guide has an installer for Mac and Windows: open it, follow the prompts, done. If you already use Node.js, you can skip the installer and let npx fetch Sidekick instead; the guide shows that route too.
3. Add Sidekick to ChatGPT
In ChatGPT, open Settings → MCP servers → Add server. Name it indesign-sidekick, choose STDIO, and under Command to launch enter:
indesign-sidekickUnder Arguments, click Add argument and enter start. Save, then let ChatGPT restart.
(With the npx route, the command is npx and the arguments are -y, indesign-sidekick and start, one at a time.)
ChatGPT shares these settings with Codex CLI, so Sidekick now works there as well.
4. Tell ChatGPT to use Sidekick
This is the step people miss. ChatGPT can also operate your computer by taking over the screen, and when you ask it to do something in InDesign it may reach for that instead of Sidekick. Screen control is slow, clumsy and blind to what is actually in your document. One line keeps it on the right track. Open Settings → Personalization → Codex instructions, paste this, and save:
For anything in Adobe InDesign, use the indesign-sidekick MCP tools rather than Computer Use, unless I explicitly ask for Computer Use.5. Use Work mode
Sidekick’s tools only show up in ChatGPT’s Work mode: the Chat | Work switch at the top of a new chat. In Chat mode, ChatGPT does not know InDesign exists. This is the other thing that makes people think the setup failed when it didn’t.
6. Check it
Give ChatGPT a few seconds after the restart. Then, with InDesign open, start a new chat in Work mode and ask:
Use Sidekick to check InDesign is connected.ChatGPT asks your permission the first time it uses a Sidekick tool. Allow it, and it should report that InDesign is connected. If it asks to control your screen instead, don’t allow it: check step 4 and start a new chat.
What happened in the video
ChatGPT planned first, then went to work: sixteen tool calls in about three minutes. It created the document with bleed, 16 mm margins and a three-column grid, generated the two photos itself, placed the soup full bleed across the left page, set the title and intro in Minion Pro, put the ingredients in a narrow column with the numbered method beside them, and dropped the roasted tomatoes in as a smaller picture.
What we liked most happened in the middle. After the first pass, ChatGPT took a snapshot of the spread, read back the position of every frame, and moved all of them onto the grid it had chosen, in one command. It did not trust its first attempt; it measured. Then another snapshot, a check for overset text, save, and it switched InDesign to Preview mode with the spread fitted to the window.
The result is a spread a designer could open and keep working on: every frame on the margins, real text in real styles, photos as linked files.
Why this works
Sidekick is not a Claude plugin. It is an InDesign plugin that speaks MCP, the open protocol AI assistants use to work with other software. Any assistant that speaks MCP can drive InDesign through it, and they all get the same tools, run the same code inside InDesign and see the same snapshots. Claude and ChatGPT can even be connected at the same time; here is how that works.