46a MCP Server

46a MCP Server

Live control of a 46a project open in a user's browser, via MCP. Lets an MCP client read live application/DOM state and perform editor actions in real time.

Installation

As an HTTP (configured outside mcpServers)

How to use the MCP connector, for hints ask claude "claude: show me where to configure mcpServers?"

1. Add the server URL as a custom connector (claude.ai: Settings → Connectors → Add custom connector; Claude Code: claude mcp add --transport http 46a-mcp https://46a.co/mcp).

Configure entry with OAuth

Local claude MCP configuration to use oauth (default)

{
  "mcpServers": {
    "46a-mcp-http-oauth": {
      "type": "streamable-http",
      "url": "https://46a.co/mcp"
    }
  }
}

Configure a entry with basic auth

Local claude MCP configuration to use basic auth instead of oauth.

{
  "mcpServers": {
    "46a-mcp-http-basic-auth": {
      "type": "streamable-http",
      "url": "https://46a.co/mcp",
      "headers": {
        "Authorization": "Basic <user:pass>"
      }
    }
  }
}

Configure stdio process (you probably won't need this)

{
  "mcpServers": {
    "46a-mcp-stdio": {
      "command": "node",
      "args": ["src/stdio.js"],
      "cwd": "/Users/jroy/src/46a/mcp",
      "env": {
        "REMOTE_URL": "https://46a.co/mcp",
        "EMAIL_OR_USERNAME": "<user>",
        "PASSWORD": "<pass>"
      }
    }
  }
}

Running (or this)

node src/http.js

Connecting a client

A. Configure a custom connector, or B. Add entries (as above) to .mcp.json or other Claude config location, using either basic auth or OAuth (default), or C. Configure a local entry for the stdio-based process (see above)

Workflow

1. listConnections → pick a live connectionId.
2. callTools and/or inject against that connectionId.

connectionId is ephemeral and orphans on page reload — re-list when in doubt.

Tools

Client discovers tools via tools/list.

• listConnections — list live browser connections. Optional emailOrUsername filter. Returns connectionId -> { user, project }.
• callTools — run 46a tool calls against one connection: { connectionId, request: { v: 't', calls: [...] } }.
• inject — run code in the connection's browser session: { connectionId, request: { v: 'j', code } }. code must be a single expression evaluating to a Promise.
• hello_world — connectivity test tool.

callTools call surface

request.calls

• add_object — add a single object (Circle, Square, _basic.text, _basic.plainText, _basic.html, SVG).
• add_objects — batched add_object, preferred for creating many objects at once.
• make_object_from_html — add an object from a raw HTML snippet.
• getSelectorData — read application state (page, workspace, project, user, objects, logs).
• doAction — perform an editor action (undo/redo, open editor, select objects, zoom, change page, patch object fields, project/page lifecycle, etc).
• createImage — generate an image via DALL-E and add it to the project.
• delegateAI — delegate a task to another assistant.
• uiInteraction — create a UI widget/interaction in the chat thread or UI.