Why AI Keeps Generating the Wrong Design Tokens and How I Fixed It with Figma's API

AI design system output is approximate by default. Wrong border radii, raw hex values, inconsistent tokens across 60 components. The fix isn't better prompts. Here's the structural change that made it exact using Figma's REST API.

The fourth time I manually corrected the same border radius mistake in an AI-generated component, I stopped and asked why this kept happening.

Not "what prompt would fix this?" The deeper question: why does every AI tool I tried get the structure right and the values wrong?

The button was correct. The variants were there. The layout matched the Figma spec. But borderRadius: 8 when it should be borderRadius: '8px'. A spacing gap of 8 when the spec said 6. The color #3B82F6 sitting in the file where semantic.button.primary should be.

None of it wrong in a way that breaks the build. All of it wrong in a way that breaks the design system.