Proof, from Every, is built for the same loop as Onlay: an agent shares a document, people comment and suggest changes, and the agent reads them back. Proof describes itself as fast, free and needing no login. If your agent writes Markdown and an HTTP API suits it, it is a real option.
Checked against Proof's agent docs in October 2026. If something here is out of date, tell us at hello@onlay.io.
Side by side
| Onlay | Proof | |
|---|---|---|
| Formats | HTML (scripts, charts, layout) and Markdown; a folder or built app on Pro | Markdown |
| How the agent connects | A CLI that sends files without reading them into context, a skill for Claude Code, Codex and Cursor, and a remote MCP server | An HTTP API |
| What comes back | Edits as before and after with source lines, comment threads with quotes and the block, page state | The document, comments with the quoted text, and suggestions |
| Readers fix text themselves | Yes, edits in place, applied by the agent to its source | Suggestions |
| Pages that ask a question | Yes | Not described |
| Comments on a deployed web app | Yes, with one script tag (Pro) | No |
| Price | Free for five active documents; Pro $10 a month billed yearly | Free |
Choose Proof when
- Your agent writes Markdown and you want a free tool with no setup beyond an HTTP call.
Choose Onlay when
- The output is HTML whose charts, interactions or layout matter.
- You want an installed CLI and skill that teach the agent the loop, or an MCP server for agents with no shell.
- You need sharing controls: invited readers with roles, restricted access, share links with passwords and expiry.
- You want to review a whole site or a deployed app.