Use 12ui from Claude, Claude Code, or ChatGPT without installing a local binary. The remote MCP server at https://mcp.12ui.com/ connects your client to the same 12ui account, quotas, runs, and owned artifacts as the web app and CLI.
The MCP path is for hosted tools and platform-managed sign-in. Prefer the CLI workflow? Install the skill, or use its optional ChatGPT plugin.
Connect
Every client points at the same server URL and finishes with 12ui sign-in and consent.
Claude (claude.ai)
Add the MCP URL as a custom connector:
- In claude.ai, open Settings, then Connectors, and choose Add custom connector.
- Name it
12uiand enterhttps://mcp.12ui.com/. - Leave the optional OAuth client ID and secret fields empty — 12ui's authorization server identifies Claude automatically. Add the connector, then complete 12ui sign-in and consent.
- Enable 12ui in a chat and confirm that Claude discovers exactly six tools.
Claude Code
Add the server, then authorize it:
claude mcp add --transport http 12ui https://mcp.12ui.com/Run /mcp, choose 12ui, and complete sign-in in the browser. Claude Code holds the token; 12ui never sees your Claude account.
ChatGPT
Add the MCP URL directly in ChatGPT:
- In ChatGPT, open Settings, then Security and login, and enable Developer mode. Availability can depend on your account or workspace policy.
- Open ChatGPT Plugins, choose the plus button, and name the connection
12ui. - Under Connection, enter
https://mcp.12ui.com/. Choose OAuth / CIMD if ChatGPT asks for a method; do not choose DCR. - Create the connection and confirm that ChatGPT discovers exactly six tools.
- Start a new chat, add 12ui from the tools menu, and complete 12ui sign-in and consent.
OAuth stays between your client and 12ui. The model does not receive your access token, refresh token, API key, or cookies. The connection uses your existing 12ui account and its normal quota or prepaid wallet.
What it can do
The connector can search the design corpus, create draft directions, plan and generate a coherent multi-screen branch, convert interface images, and read durable progress and artifacts. It returns owned images as authenticated original resources rather than public links or bulk inline data.
The MCP server is a remote adapter over the shipped 12ui product. It does not create a second pipeline, billing identity, quota, or artifact store.
The six tools
| Tool | What it does |
|---|---|
draft | Creates and settles one to four interface directions from a concept and optional references. |
branch_execute | Plans a coherent multi-screen branch from an owned draft candidate or source image. It creates the plan, not the screens. |
branch_next | Generates the next dependency-ready group of screens. Repeat only when the returned next action directs it. |
convert | Starts an asynchronous conversion from an image, owned LayerDoc, or successful conversion into a supported 12ui output. |
corpus_search | Retrieves a durable, varied set of visual references from the 12ui corpus. |
run_status | Reads progress, errors, images, artifacts, and the next action for an owned run. It never starts or pays for work. |
Runs and paid work
Corpus search is free within its daily and per-minute limits and never uses prepaid funds. Draft, branch, and conversion calls can use their daily allowance or prepaid funds. If a paid call is interrupted or its result is uncertain, reuse the same idempotency key and arguments. A new key can buy the work again.
branch_execute returns after the plan is durable. Follow its branch_next actions until every dependency-ready group is settled. convert can continue asynchronously; use run_status until it reaches a terminal state. A status read never dispatches, retries, regenerates, or pays for work.
Images and limits
- Inputs support PNG, JPEG, and WebP as inline data or a public HTTPS URL, up to 6 MB through MCP.
- Generated originals are authenticated resources tied to your account. A client reads one resource at a time.
- 12ui never silently resizes, recompresses, or swaps an original to fit the MCP limit.
- Use the web converter or CLI for larger images and local-file workflows.
MCP or CLI
| Use MCP when | Use the CLI when |
|---|---|
| Claude or ChatGPT should manage OAuth and call hosted tools without a local binary. | Your agent can run a binary and needs local input, output, packaging, or prototypes. |
| Remote run IDs, status, and authenticated resources are enough. | You need full project materialization, filesystem continuations, or transfers above 6 MB. |
Never start the same paid intent through both paths. If you move between them, keep the existing run or conversion ID and the original idempotency identity.