Keyline MCP server cuts agent token use 2-6x by replacing HTML screenshots with JSON scenes

yuvalt · reddit · 2026-10-05

Problem: agents building social ads via HTML + headless Chrome screenshot loops (screenshot, spot clipped headline, fix, repeat) burn tokens and can't do animation.
Solution: keyline, a single-binary Rust MCP server built on Skia with no browser. The agent writes a small JSON scene; keyline lays it out at every requested size and returns structured errors like leaderboard content !overflow needs 572×116, so the agent fixes issues without screenshots.
Results: in the author's benchmark (same model, two tasks, 5 runs each) it used 2x fewer tokens than HTML + headless Chrome and 6x fewer than Playwright MCP. All runs are published.
Motion: supports letter-by-letter fly-ins, keyframes, video clips with sound, and transitions; outputs MP4, WebM, GIF, or animated PNG — e.g. an Instagram post, a 300×600 banner, and a 6-second story in one go.
Open source: keyline.dev, repo at GitHub keyline-dev/keyline.

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