3dstreet

What 3dstreet MCP server does

The 3dstreet MCP server connects an MCP client to a 3DStreet editor tab running in a browser. It exposes scene inspection, entity selection, camera control, entity changes, and undo or redo through MCP tool calls. The listed tools are getScene, getEntity, getSelectedEntity, selectEntity, focusCamera, entityCreate, entityUpdate, entityRemove, undo, and redo.

The browser tab performs the actual scene operations. This makes the relay useful for desktop or command-line agents that cannot use WebMCP directly. A browser-native agent that supports WebMCP can instead open 3dstreet.app and use the page-registered tools without installing this package.

How it works

The client starts the relay as a stdio MCP process. The relay then bridges MCP tools/list and tools/call requests to a 3DStreet tab over WebSocket at 127.0.0.1, using port 51735 by default. When a tab pairs, the relay obtains the tool list from that tab, so the available registry can change with the connected editor build.

Pairing starts from a URL printed by the relay, such as https://3dstreet.app/#mcp. Opening it in a signed-in browser causes the editor to open its AI Assistant pane and connect automatically. Manual pairing is also available from the AI Assistant pane with /mcp and Reconnect. Only one browser peer can occupy a relay at a time; a second connection is rejected.

The relay handles MCP initialization and ping messages locally while forwarding tool requests. If no tab has connected during the current session, a tool call fails quickly with the pairing URL. After a tab has paired, temporary disconnections can wait for reconnection and then complete pending calls.

Setup and configuration

Install or run the 3dstreet MCP server through npx -y 3dstreet-mcp. In Claude Desktop, add it as an MCP server in the platform configuration file and restart the application. In Claude Code, run claude mcp add 3dstreet -- npx -y 3dstreet-mcp. Cursor is also identified as a client without browser or WebMCP support.

The command supports --port for selecting another WebSocket port and --origin for changing the origin used in the pairing URL and MCP instructions. Use a different port when connecting separate clients to separate tabs. For local 3DStreet development, set the origin to the local development server, such as http://localhost:3333.

Limitations and notes

The 3dstreet MCP server is alpha software, so its protocol may change. The relay binds only to localhost and accepts WebSocket upgrades from the documented 3DStreet and local development origins. Authentication tokens do not cross the WebSocket; the connected browser tab owns the signed-in session, catalog, and cloud-save flow.

Scene creation works in any 3dstreet.app tab, while saving and geospatial functionality require a free 3DStreet account. The editor includes a Read-only toggle that blocks scene mutations when enabled. Browser clients with WebMCP support do not need this relay, and the project is expected to be retired when those clients can use WebMCP natively.