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Quiet Pixel
1 month ago

figma mcp invented a --space-13 token and wrote a 200-line "cleanup"

#tooling#mcp#design
Figma
Fetch Figma design context via MCP and turn nodes into code

connected figma mcp to cursor last night. asked it to pull our button styles from the real file.

it invented --space-13 (we don't have that), renamed half the variants to ButtonPrimaryNew2, then opened a PR with 200 lines of "cleanup". figma desktop was still open on my m2. the node ids it cited were from a deleted page.

anyone got a prompt/rule that keeps it from hallucinating tokens, or do we just treat mcp export as a sketch?

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  • Sasha

    yeah this bit me last week. agent kept inventing color/brand/hover-alt that was never in the file. i started pasting the exact node url + "only use tokens that exist in variables.json" in the prompt. still drifts after ~3 turns tho.

    treating the export as a sketch is the right call imo. i never merge its PR without a human pass on the tokens.

    • Nina Brooks

      curious what this costs you in tokens when it goes off the rails. our design handoff loop burned ~$18 one afternoon just renaming buttons nobody asked for. do you cut the session after 3 turns or keep going?

      • Sam R

        we hit ~$12 on a single component pass once — mostly because it kept re-reading the whole file. i kill the session after 2 loops now and open a fresh one with just the frame url.

        do you log token use per figma node or is that overkill

    • Pixel

      same. i dump the variables csv into the chat and say "if its not in this list, stop". lasts maybe two turns.

      you merge the sketch prs with a human pass every time or only when tokens change?

  • Aya

    we pin a tokens.json export and tell the agent it's read-only. still invented --radius-pill-lg twice.

    also check keyboard focus after its "cleanup" — last time it nuked :focus-visible on our secondary button. pixel diffs caught the color drift; a11y didn't.

    • Wei Zhang

      Focus-visible delete is nasty. We added a tiny playwright check that fails if any button or a loses :focus-visible after the agent PR.

      Also — does your tokens.json pin include the deleted-page node ids? Ours kept citing ghosts until we wiped the MCP cache.

  • Priya Raman

    I ban the MCP from writing tokens.json at all now. Read-only export, then I hand-map the three buttons I actually need.

    --space-13 is almost funny until legal asks why the live site has spacing that doesn't exist in the brand doc. Cursor + Figma MCP is a moodboard, not a token source of truth.

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