Build Design skill

Build design

This skill turns a design into code that matches it. It reads the design at its source, builds with what the project already has, then compares the result against the design before calling it done.

The design decides. Values come from the design file, never from your taste or a pattern you liked elsewhere. A change the design does not show is a deviation, and a deviation is the user's call.

It owns no domain rules. Where the design breaks one, build it as designed and report the conflict with its owner. Contrast is a requirement in better-accessibility and a measurement in better-colors. Focus and semantics are better-accessibility, type is better-typography and spacing and structure are better-layout. Palette is better-colors, copy is better-writing and surfaces, icons and motion are better-ui. Reviewing finished work is interface-review, exploring alternatives is variant and stress testing a component is break.

1. Read the design at its source

A Figma link means the Figma MCP. Search the available and deferred tools for figma before saying it is unavailable, since the server often sits under a name you did not expect. A server that lists only an authenticate tool is connected but signed out, so ask the user to authenticate. With no Figma tool at all, ask the user to connect one, and do not build from memory or guesswork meanwhile. figma.md holds which tools to call and what each returns.

A screenshot or exported image has no values to read. Sizes are ratios to the capture, so state the scale you assumed and treat every measurement as an estimate. Ask for the Figma link when one exists, since it replaces the whole estimate.

Scope the run to the frames named. Frames that show the same thing at different widths are one piece at several breakpoints, not separate pieces.

This step is done when you hold a screenshot of every frame in scope and its values for spacing, size, radius, color, type and the components used. From a Figma file they are exact. From an image they are estimates at the scale you stated.

2. Map the design onto the project

Read the project's tokens and component library before writing anything. Then map every design value to what exists:

In the design	In code
A bound variable or style	The token with the same name or the same value
A raw value that equals a token	That token
A raw value with no token	The nearest existing token, listed in the report as rounded
A component instance	The project's component of that name, with the variant the design shows
A component instance with no project equivalent	Plain markup in place, listed as a deviation, and ask whether a component should exist
A one-off group of layers	Plain markup in place, not a new component

Never add a token, a component variant or an arbitrary value to hit a number. Stop and ask which way to go when rounding would visibly change the design. That means more than 2px on spacing or size, or a color landing on a different step.

Check what data the design needs and wire it to what exists. Where the backend for part of it does not exist yet, build that part as UI fed by props and name it in the report as unwired.

3. Build only what the design shows

Implement the frames, the breakpoints the frames define and the states the file draws, such as hover, empty or error. A state the file does not draw is not yours to design. Leave it to the existing component's default and list it as missing.

Leave everything around the piece as it was. No neighbouring copy edits, no icon swaps, no "while I was here" cleanups. A diff wider than the design is the most common way this goes wrong.

4. Compare against the design

Render the build at each frame's width beside the design screenshot and walk it element by element. Compare the properties Read the design at its source collected. "Gap is 12px, design is 16px" is a finding. "Feels a bit tight" is not.

With a browser at hand, screenshot each width and compare. Without one, hand over the local URL with the widths to check and say the comparison is unverified. Do not report a match you did not look at.

Fix every mismatch you caused, then compare again. This step is done when every remaining difference is a rounding or a question.

5. Report and stop

Element	Design	Built	Status
Card padding	20px	p-5	Matches
Title size	15px	text-sm, 14px	Rounded to token
Badge	Filled pill	Text label	Deviates, asked: no badge component exists

Then list, one line each, and omit a list with nothing in it:

• Unwired. What renders from props until the backend exists.
• Missing states. What the design does not draw.
• Domain conflicts. Where the design breaks a rule, with the owning skill.

Close by saying where the build is running and at which widths you compared.

Before you finish

You notice	Fix
"Figma isn't connected" written before any tool search	Search the tools for figma first
Values in code that appear in no Figma response, only in the screenshot	Read them from the design context
An arbitrary utility such as w-[343px] or a raw hex in the diff	Map it to a token, or ask if rounding shows
A new file under the components directory for a frame that is not a component	Inline it as plain markup
A loading or error branch the design never drew	Remove it, keep the default and list it as missing
Files in the diff that no frame touches	Revert them
A contrast or focus change the design does not show	Restore the design and report the conflict with its owner
A comparison claimed with no screenshot of the build	Render each frame width, or say it is unverified
Hard-coded sample data with no mention in the report	List it under Unwired