RoomDex

RoomDex began with one concrete request: move only the floor lamp to the other side of the chair. Room design is iterative, but an agent working from a screenshot has to guess at scale and translate intent into mouse movements. A generated image leaves nothing precise to refine.

RoomDex is a client-only room-planning workspace where a person and an agent work on the same measurable 3D room. The visible room exposes 21 native WebMCP tools. The agent can inspect the room, compare three arrangements without changing anything, measure clearances, apply a layout, place wall art, move or style named furniture, analyze spatial constraints, review recent work, and undo a specific change.

WebMCP is central because it exposes product meaning rather than screen coordinates. A tool such as move_furniture accepts a named object, real measurements, a relationship, and an expected revision. Every successful write updates the visible room, records whether a person or agent made it, and creates an undoable revision. Reads do not mutate the room. RoomDex checks collisions, boundaries, clearances, circulation paths, and fixed openings.

The demo shows the agent inspecting the room, comparing arrangements, applying a reading corner, creating measured procedural wall art in opening-safe space, moving only the floor lamp to exact coordinates, analyzing the result, reviewing recent changes, and undoing only that move.

React and TypeScript provide the interface and state boundary. Three.js renders procedural furniture. A serializable domain engine owns room geometry, spatial validation, activity, and history. One declarative WebMCP registry supplies the native document.modelContext.registerTool path and the local evaluation bridge. Writes are serialized and wait for the matching rendered revision before completing.

Codex supported research, implementation, testing, native-browser verification, accessibility, security, performance, deployment, and release QA. The final release includes 211 deterministic tests across 19 files. All 21 native tools were verified on the public Vercel deployment in Codex's in-app browser.

To test it, open https://roomdex.vercel.app/ in ChatGPT's in-app browser or Chrome with WebMCP enabled and confirm the toolbar says 21 agent tools. Ask the agent to inspect the room and compare all three built-in arrangements without changing it. Then ask it to apply the reading-corner arrangement, add a warm geometric print, move only the Floor lamp, analyze the layout, review recent changes, and undo only the lamp move.

Built With

• openai-codex
• react
• three.js
• typescript
• vercel
• vite
• vitest
• webmcp