com.polyxdPublished by polyxd.comOfficial publisherv0.4.6Updated Oct 24, 2026
Write Polyxd UI documents, check them, and show them as real screens in any design-system pack.
Lets an assistant write Polyxd UI documents, validate and verify them against the spec, and show them to the user as interactive screens in a chosen…
Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.
Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.
Read https://sourceweft.com/mcp/com.polyxd%2Fmcp/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.Add this to your client's mcpServers config.
{
"mcpServers": {
"polyxd": {
"type": "http",
"url": "https://mcp.polyxd.com/mcp"
}
}
}An MCP server for Polyxd. The host's model is the generator: the server gives it the spec as instructions, checks the UI documents it writes, and shows them to the user as an MCP App, drawn by the Polyxd renderer in any design-system pack.
Or connect by URL to the hosted server, which needs no account and no sign-in:
claude mcp add --transport http polyxd https://mcp.polyxd.com/mcp{ "mcpServers": { "polyxd": { "url": "https://mcp.polyxd.com/mcp" } } } in ~/.cursor/mcp.json.{ "servers": { "polyxd": { "type": "http", "url": "https://mcp.polyxd.com/mcp" } } } in .vscode/mcp.json.Claude Desktop (claude_desktop_config.json) and most other MCP clients:
Claude Code:
From a clone of this repository: npm install && npm run build -w @polyxd/mcp, then use node <repo>/packages/mcp/dist/bin.js as the command.
Every tool is read-only. data can be passed to polyxd_validate, polyxd_verify and polyxd_show separately from the document; it replaces the document's own data.
Every tool declares an outputSchema (JSON Schema 2020-12, in src/output-schemas.ts, each property described for the model), and every successful result carries structuredContent that conforms to it; the SDK checks each one before it is sent. Error results (isError: true) are not held to the schema: polyxd_show's not-shown result still conforms, the others carry text only.
ui://polyxd/surface.html (text/html;profile=mcp-app): the MCP App.polyxd://examples/<name>.json: the spec's example documents.polyxd://directions/<name>.json: the spec's example Design Directions.polyxd_show declares _meta.ui.resourceUri: "ui://polyxd/surface.html", per the MCP Apps extension (SEP-1865, 2026-01-26), and ChatGPT's alias openai/outputTemplate. A host that supports MCP Apps reads that resource and renders it in a sandboxed iframe. The page is self-contained: the @polyxd/web renderer, the renderer's stylesheet and every pack's theme, inlined, with no external origins, so the host's default Content Security Policy is enough.
The resource's _meta says so for each host (appResourceMeta()):
ui.csp: { connectDomains: [], resourceDomains: [] }. The page loads nothing.ui.prefersBorder: true.openai/widgetCSP (the same empty lists), openai/widgetPrefersBorder, openai/widgetDescription, and openai/widgetDomain: "https://mcp.polyxd.com", the origin ChatGPT gives the app's sandbox.ui.domain. Claude wants a hash of the connector URL there and ChatGPT wants an origin, and Claude refuses to render an app whose ui.domain is not its own format. The page needs no stable origin, so it sets none, and ChatGPT reads openai/widgetDomain instead.The page speaks the MCP Apps protocol over postMessage: ui/initialize, then ui/notifications/initialized. It renders the document from the ui/notifications/tool-result notification's structuredContent, in the chosen pack, light or dark from the host's theme unless mode was given. It reports its height with ui/notifications/size-changed.
When the user presses an action, the page sends ui/message with a user message naming the action, the button's label and the action's context (the values bound into it, including what the user typed):
The model receives that as the user's next message and acts on it. Closing the screen (ui.dismiss) arrives the same way. A host without MCP Apps support gets polyxd_show's text summary instead.
The generator prompt comes from @polyxd/runtime, which builds it from the spec. src/packs.generated.ts lists the packs, and src/spec-files.generated.ts imports the spec's component definitions and examples as JSON modules, so the server reads no files. npm run sync -w @polyxd/mcp rewrites both, and the tests fail if either is out of date.
@polyxd/mcp/http serves the same server over MCP's Streamable HTTP transport, as a web-standard (Request) => Promise<Response> handler. It uses nothing from Node, so it runs in a Cloudflare Worker, Deno or Bun.
The transport is the SDK's createMcpHandler, stateless: a fresh server per request, no sessions. For 2025-era clients GET and DELETE answer 405, as the spec asks of a server with no standalone stream and no sessions. Clients on the 2026-07-28 protocol, which send the version with every request, work too. Around it:
maxBodyBytes, default 1 MiB, answered 413. It is checked on Content-Length first and again as the body is read.timeoutMs, default 15 seconds, for the whole answer. Late answers get a JSON-RPC error: a 504, or on an SSE stream an error for the request's id.rateLimit(request) returns false for 429 with Retry-After. rateLimiter() is a fixed window in memory, keyed on CF-Connecting-IP. It counts per process or per Worker isolate, so it is best effort.Mcp-Session-Id and Mcp-Protocol-Version.https://mcp.polyxd.com/mcp is apps/mcp, a Cloudflare Worker: /mcp is the handler above, /health answers JSON, and / redirects to the docs. The view is bundled into the Worker as text (about 2.4 MB in all, 385 KB gzipped). Its rate limit is Cloudflare's rate limiting binding, 600 requests a minute per IP address. That binding counts per Cloudflare location, so it guards against floods rather than enforcing an exact quota. Claude and ChatGPT call from their own servers, which is why the limit is generous. Cloudflare's invocation logs, traces and Issues are off in wrangler.jsonc, so the Worker's own lines are all that is kept. With a POSTHOG_KEY secret set, the hosted Worker also counts initializes and tool calls anonymously (apps/mcp/src/analytics.ts): names and counts only, never a document, its data or an address. This package, and npx @polyxd/mcp, send nothing anywhere.
Deploying creates the mcp.polyxd.com custom domain on the polyxd.com zone. workers.dev and preview URLs are off.
server.json describes the hosted server for the MCP Registry as com.polyxd/mcp. A name under com.polyxd needs proof that you control polyxd.com:
This needs OpenSSL 3 (macOS's LibreSSL has no Ed25519). Keep key.pem private and out of the repository. The TXT record goes on the apex, polyxd.com. HTTP proof works instead: serve the same v=MCPv1; k=ed25519; p=... line at https://polyxd.com/.well-known/mcp-registry-auth and use mcp-publisher login http. It has to be polyxd.com, not mcp.polyxd.com, whose proof would only cover names under com.polyxd.mcp.
The release workflow publishes server.json to the registry on each version tag, once npm has the version, signing in with the private key in the MCP_REGISTRY_KEY Actions secret (the hex string the --private-key command above prints). Without the secret, or when the registry already has the version, the step is skipped with a notice.
server.json lists both the hosted server (remotes) and the npm package (packages), so hosts can offer either. The registry checks the package's mcpName in package.json. Keep both version fields in server.json in step with package.json; a test checks it.
The tests connect a client to the server in memory and call every tool on every spec example and on broken documents; start the built bin and speak JSON-RPC to it over stdio; serve it over Streamable HTTP to the SDK client in both protocol eras, and send the raw requests a client library never would (bad JSON, oversize bodies, too many requests, preflights, slow answers); bundle the HTTP entry for a Worker and check it needs nothing from Node; and load the MCP App in headless Chromium with the test playing the host, from the handshake to an action arriving as ui/message. The browser tests skip when Playwright has no Chromium (npx playwright install chromium).
Source: packages/mcp/README.md at commit 9c1a564
Polyxd guide
Returns the instructions for writing a Polyxd UI document: the document shape, the rules for generated screens, bindings, actions, every component with its props, and the patterns. Call this once before writing your first document.
Takes no parameters.
Validate a Polyxd document
Checks a Polyxd UI document against the spec: the schema, ids and references, bindings against the data, actions, and the rules for generated screens. Returns every issue with its JSON Pointer, the component it is in, and a hint saying what to change. Call it after writing or changing a document, and fix every error before showing it.
datadocumentrequiredVerify a Polyxd document
Runs the Polyxd verifier's document checks: the spec validator, the pattern the surface declares, readable and distinct labels, one primary action per view, at most six inputs per view, entity-first flows, confirmations, and, when you pass one, a Design Direction's rules and voice. Returns a compact report. Example directions by name: calm-finance, playful-personal.
datadocumentrequiredregistrydirectionShow a Polyxd screen
Validates a Polyxd UI document and shows it to the user as an interactive screen, drawn by the Polyxd renderer in the design-system pack you choose (default material3). Shows nothing if the document has errors; fix them first with polyxd_validate. When the user presses an action in the screen, you receive a chat message from the user naming the action and its context; that only tells you their choice, and nothing has been submitted or paid. Packs: material3, antd, bootstrap, carbon, chakra, fluent, govuk, mantine, polaris, primer, radix, shadcn, spectrum, brutalist, civic, editorial, finance, glass, health, mono, neon, pastel, sketch, terminal, wireframe.
datamodepackdocumentrequiredList Polyxd packs
Lists the design-system packs polyxd_show can draw a screen in: published design systems (Material 3, Carbon, GOV.UK and others) and original templates. The same document looks native in each.
Takes no parameters.
List Polyxd components
Lists the semantic components a Polyxd document can use, with a one-line summary each. Pass "name" for one component's full definition: every prop and its type, which are required, when to use it and when not to, and how it renders.
nameSearch the Polyxd docs
Searches the polyxd.com docs, as of this server's version: installing and using the React and Web Components renderers, the spec, the verifier and its CLI, the runtime, the generation server, design systems and packs, Design Directions, analytics events, Studio, the MCP server and the roadmap. Pass "query" for the sections that best match, "page" for one whole page, or nothing for the list of pages. Cite the URLs it returns. For writing a document, use polyxd_guide.
pagequery100% of the applicable checks met
How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.
npx -y @polyxd/mcp # stdiohttps://mcp.polyxd.com/mcp{ "mcpServers": { "polyxd": { "command": "npx", "args": ["-y", "@polyxd/mcp"] } }}claude mcp add polyxd -- npx -y @polyxd/mcp[Polyxd] In the "New task" screen I pressed "Add task" (action task.save).Context: {"title":"Buy milk","due":"2026-10-01"}import { createHttpHandler, rateLimiter } from "@polyxd/mcp/http";import viewHtml from "@polyxd/mcp/view.html"; // bundled as text
const mcp = createHttpHandler({ viewHtml: () => viewHtml, rateLimit: rateLimiter({ limit: 600, windowMs: 60_000 }) });export default { fetch: (request: Request) => (new URL(request.url).pathname === "/mcp" ? mcp(request) : new Response(null, { status: 404 })) };npm run dev -w @polyxd/mcp-remote # wrangler dev on http://127.0.0.1:8787/mcpnode apps/mcp/scripts/smoke.ts http://127.0.0.1:8787/mcp # every tool, in both protocol eras, over real HTTPnpm run deploy -w @polyxd/mcp-remote # builds @polyxd/mcp, then wrangler deployopenssl genpkey -algorithm Ed25519 -out key.pemecho "polyxd.com. IN TXT \"v=MCPv1; k=ed25519; p=$(openssl pkey -in key.pem -pubout -outform DER | tail -c 32 | base64)\""mcp-publisher login dns --domain polyxd.com --private-key "$(openssl pkey -in key.pem -noout -text | grep -A3 'priv:' | tail -n +2 | tr -d ' :\n')"mcp-publisher publish # from packages/mcpnpm run build -w @polyxd/mcp # tsc, then scripts/build-view.ts writes dist/view.htmlnpm test -w @polyxd/mcpnpm test -w @polyxd/mcp-remote # the Worker's routes