An agent writes a plan. You open it, read it, mark it up, edit a few lines, and hand it back. Markdown is a small Mac app that makes that half of the loop pleasant, and makes sure nothing you do damages the other half. It is also where I take my notes.
I am a big fan of the Markdown format, which John Gruber created in 2004. It is simple and elegant. I started using a lot of Markdown files once I began building with AI agents: they are perfect for writing designs and plans and for recording status and bugs, for me and for the AI agents. For now, they are the perfect human-machine interface.
I used VS Code to read them, but it is too heavy and overbuilt for that, and I did not find anything I liked. So I built this simple viewer and editor. It also serves as my note taker.
A thought before it goes, the to-do list for today, a brief for the agent. Cmd+N, a heading, a few lines, save. The file lands in the folder you are in, named from the heading. No template, no dialog, no vault to set up, no account. Tick a box when a task is done. A note is a plain Markdown file on your disk, so an agent can read it tomorrow and so can you in twenty years.
Pick a paper and a typeface once, then there is nothing between you and the text. The app does not badge, does not nag, and does not ask you to reload. It stays quiet until you have something to say.
VS Code reads Markdown along with everything else, and carries everything else with it. Obsidian is a vault with a graph and a plugin ecosystem, a second brain that needs tending. Notion and Apple Notes keep your writing in their database, where an agent cannot reach it. Typora and iA Writer are lovely to write in, and were designed before agents began writing files next to you.
Markdown is a folder of plain files, an editor that stays out of the way, and an app that expects an agent to be reading and writing beside you. That is the whole idea.