---
title: "Apply your design system guidelines in v0"
description: "Connect v0 by Vercel to UI Rules as a custom MCP connection, so it builds to your brand and design system guidelines rather than its own defaults."
label: "v0"
date: "2026-10-05"
---

v0 takes a custom MCP connection. Once connected, v0 can read your brand styles, rules, and component vocabulary while it builds.

You sign in to UI Rules as part of the setup, so there is no key to copy. The **Connect** dialog in the workspace top bar shows the same steps when you pick **v0**.

## Add the connection

<Steps>
<Step>
### Open the MCP form

In a v0 chat, click **+**, then **MCPs → Custom MCP**.
</Step>
<Step>
### Fill in the form and sign in

Paste the name and URL, select **OAuth**, and click **Authorize**. Approve the project in your browser.

- **Name**: `UI Rules`
- **URL**: `https://mcp.uirules.com/mcp`
</Step>
<Step>
### Tell v0 to use it

This step is not optional. Without it, v0 designs first and consults your brand afterwards.

Open **+ → Instructions → New Instruction**. Add a title, paste this rule, click **Add**, and keep it checked.

```text
Before any UI work, call the UI Rules MCP tools get_brand_brief, get_project_notes, get_rules_index and get_design_tokens, in that order. Do not generate design inspiration or choose a visual direction; the brand's rules and tokens are the design direction. Every word of copy you write is governed too: call get_rules for the area covering writing before you write any text. Run check_rule_compliance at the end and report what it returns.
```
</Step>
<Step>
### Check the connection

Ask **"Is UI Rules connected?"** to check.
</Step>
</Steps>

## Troubleshooting

If v0 does not connect or ignores your brand, see [Troubleshooting](/docs/connect/troubleshooting).