MCP App Dev Kit

Build & prototype MCP apps (tools + UI views) for Portkey Mission Control, locally, then test them live in Claude Desktop over ngrok. A skybridge fork with real local Durable Object storage (DO SQL) and a driver skill so Claude can build apps end-to-end.

Quick start

npm install
npm run dev          # skybridge dev — fast UI iteration (in-memory store). MCP at :3010/mcp, DevTools at :3010/
# or
npm run dev:do       # skybridge build && wrangler dev — REAL local DO (DO SQL, persisted). Use to test persistence
                     # + for the Claude Desktop connector.

Render views without an LLM at http://localhost:3010/ (the DevTools). To use in Claude Desktop: ngrok http 3010 → add https://<x>.ngrok-free.app/mcp as a custom connector (Auth: None).

Related MCP server: Remote MCP Server (Authless)

The skill (how Claude builds apps)

skills/mcp-app-dev/ is the mcp-app-dev skill (forked from skybridge's mcp-app-builder). Install it in Claude Desktop; it drives the whole loop: scaffold tools+views → run the dev server → ngrok → connect → iterate. Start at skills/mcp-app-dev/SKILL.md; app-authoring guidance is in skills/mcp-app-dev/references/.

Layout

src/server.ts     # MCP server — register tools (one view-bearing tool per view)
src/store.ts      # getStore() — DO SQL under wrangler, in-memory under skybridge dev (same app code)
src/task-do.ts    # the Durable Object (DO SQL) — the example app's table + methods
src/views/*.tsx   # one React view per view-bearing tool (file name = view.component)
cf-entry.ts       # worker entry for wrangler: re-exports skybridge's handler + the DO class
wrangler.jsonc    # DO binding + the load-bearing compat config (date >= 2025-09-01, define NODE_ENV)
deploy.mjs        # build + split modules[] (→ DO facet) / assets[] (→ R2); push to PMC is stubbed (see DEPLOY.md)

The kit ships an example Tasks app — replace it with your app (the skill walks you through it). It's a plain MCP app (tools served directly, per-tool views — no shell wrapping), which is what deploys cleanly to PMC.

Storage = DO only

DO SQL / DO KV only — no D1, no external DBs (PMC's model). All data goes through getStore() so it runs in both dev modes and maps onto a PMC app-host facet. See skills/mcp-app-dev/references/persistence.md.

Deploy

node deploy.mjs --base <your-PMC-url> --slug <app-slug> splits the build (facet → modules, view → assets/R2) and ships it to PMC via app.builder.deploy; the deployed app serves through the shell connector. The PMC URL is never hardcoded — pass --base (or PMC_URL); ask the user for it. See DEPLOY.md.