App Inventor MCP

An MCP (Model Context Protocol) server that lets AI agents build and edit MIT App Inventor projects. The agent creates real .aia files on disk, which you then import into App Inventor via Projects > Import (.aia).

Part of the AIA Stitch family. Sister project: aia-stitch (web UI for merging projects).

Why

App Inventor is a visual drag-and-drop tool, which historically locked out AI agents. But an .aia file is just a zip: screens are JSON documents (*.scm), blocks are XML (*.bky), assets are plain files. This server exposes those facts as tools any MCP client can call, so an agent can scaffold an entire multi-screen app for you before you ever open the designer.

Setup

Requires Node 18+.

npm install
node server.mjs

Add to your MCP client config (Claude Desktop, opencode, etc.):

{
  "mcpServers": {
    "app-inventor": {
      "command": "node",
      "args": ["/absolute/path/to/app-inventor-mcp/server.mjs"]
    }
  }
}

Tools

Tool	What it does
aia_create_project	New .aia with a Screen1, valid properties
aia_add_screen	Add a screen
aia_inspect	List screens, components, assets, properties
aia_get_screen	Read one screen's components, properties and blocks XML
aia_add_component	Add a component, optionally nested in a parent arrangement
aia_set_property	Set a property on the screen or a component
aia_set_blocks	Replace a screen's blocks XML
aia_add_event_handlers	Generate event handlers (when Click do...) without knowing Blockly XML
aia_add_asset	Embed a local file (image, sound) into the project
aia_merge	Merge multiple .aia files into one

Testing

node test.mjs    # library roundtrip: create, author, merge
node smoke.mjs   # full MCP protocol handshake + tool calls over stdio
node stress.mjs  # scale (25 screens / 120 components), concurrency, abuse, recovery

Honest limits

Components and screen properties are fully supported. Blocks authoring works at two levels: generated event handlers via aia_add_event_handlers (property setters and screen navigation), or raw Blockly XML via aia_get_screen / aia_set_blocks. There is no high-level vocabulary for every block type yet. UI-first apps work end to end today; exotic logic may want finishing touches inside App Inventor.

All file operations are serialized per path inside the process, so pipelined/concurrent calls from an agent are safe. Cross-process access to the same .aia at the same time is not guarded; don't edit one file from two servers at once.