If your AI assistant supports WebMCP, it can write Markdown straight into this editor and you read it in the live preview on the right — no more copying it out of a chat window paragraph by paragraph.
Ask an AI to write a document and the output is usually stuck in a chat window: the column is narrow, tables get squeezed, you have to select and copy it yourself, and then reflow it after pasting. The longer the document, the worse it gets.
WebMCP changes where the output goes. The AI no longer prints a copy for you to read — it writes into the editor. The width limit disappears, the live preview just works, and you edit whichever paragraph you want in place.
WebMCP is a draft web standard at the W3C (edited by Microsoft and Google) and still experimental, so support will keep moving. Where things stand today:
| Client | Status |
|---|---|
| Codex / the browser built into the ChatGPT desktop app | Works as-is, no setup |
| Chrome 149 and later | Works — this site is enrolled in Chrome's trial through 2026-11-17 |
| Edge 150 and later | Also in trial, but through Microsoft's own enrolment, which this site has not joined |
| Firefox / Safari | Not supported yet |
On a browser that doesn't have it, the whole thing silently does not exist and every other part of the editor behaves exactly as before.
| Tool | What it does |
|---|---|
mdeditor_get_outline | Reads the heading outline and length of the current document |
mdeditor_get_document | Reads the whole document, or just one named section |
mdeditor_set_document | Writes content (replace everything / append / prepend) |
mdeditor_replace_section | Rewrites only the section under one heading |
write it into the editor"
For long documents, ask it to change one section only. The AI will switch to
mdeditor_replace_section, which leaves every other word untouched — much safer than
resending the whole file.
It won't save for you. The AI only writes into the editor; the file on disk is still yours to
save with Ctrl+S. Overwriting the original is irreversible, so that keystroke stays with a human.
It won't send your files anywhere. All four tools run inside your browser. There is no backend and no upload. The AI can read the document currently open in the editor — not your whole folder.
It won't lose your work. Writing goes through the browser's native editing operation, so
Ctrl+Z still undoes it. If you think the AI made things worse, just undo.
AI models often insert their own line breaks around 70–80 characters. That doesn't affect the preview — a single newline inside a Markdown paragraph never becomes a line break — but once you save the file, line widths are ragged and changing one sentence means hunting across lines.
So on write, hard breaks inside paragraphs are joined back up. Code blocks, tables, lists, headings, YAML front matter, and the hard breaks you typed on purpose (two trailing spaces or a backslash) are all left alone. No stray space appears between CJK characters, and one is added at a CJK/Latin boundary.
If you don't want any of this, ask the AI to pass unwrapHardBreaks: false and the text is
written exactly as sent.
WebMCP is still an experimental web standard; both the spec and browser support may change. Nothing else in this editor depends on it — without it, everything works as before.
Download this page as .md Open it in the editor and you have a ready-made sample document.