Apply your design system guidelines in v0
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.
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
Open the MCP form
In a v0 chat, click +, then MCPs → Custom MCP.
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
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.
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.Check the connection
Ask "Is UI Rules connected?" to check.
Troubleshooting
If v0 does not connect or ignores your brand, see Troubleshooting.
