Swing

An MCP (Model Context Protocol) server for interacting with Java Swing applications — inspired by chrome-devtools-mcp, but targeting any Swing UI instead of HTML pages.

Modules

• swing-mcp-server — Spring Boot MCP server (stdio transport) exposing Swing automation tools.
• swing-mcp-agent — Java agent loaded into the target Swing JVM (at launch via -javaagent, or dynamically by PID). Runs a localhost-only JSON line-protocol socket server that executes commands on the Swing EDT.
• swing-mcp-common — Shared command/DTO types between server and agent.
• swing-mcp-demo — Demo Swing application used for integration testing.

How it works

MCP client (stdio) ──▶ swing-mcp-server ──localhost socket──▶ swing-mcp-agent (inside target JVM) ──▶ Swing EDT

1. The MCP client calls launch_app (starts a JVM with the agent preloaded) or attach_to_app (loads the agent into a running JVM by PID).
2. The agent binds a loopback-only port in swing.mcp.agent-port-min..max and reports it back through a response file.
3. Tools such as take_snapshot, click, and fill are forwarded as JSON line commands and executed on the Event Dispatch Thread.

See docs/tools for the full tool documentation (per-category pages), or docs/tool-reference.md for the single-page quick reference.

Skills

The skills directory contains agent skills (SKILL.md files) that teach AI coding agents how to use Swing MCP effectively — core workflows, UI testing patterns, and troubleshooting.

Building

Requires JDK 21+ and Maven.

mvn verify

GUI integration tests are skipped in headless environments; CI runs them under xvfb.

Running

Build everything, then register the server with your MCP client (see docs/installation.md for per-client instructions — IntelliJ IDEA, VS Code, Claude Desktop, Claude Code, Cursor, Windsurf):

{
  "mcpServers": {
    "swing": {
      "command": "java",
      "args": ["-jar", "/path/to/swing-mcp-server-1.0.0.jar"],
      "env": {
        "SWING_MCP_AGENT_JAR": "/path/to/swing-mcp-agent-1.0.0.jar"
      }
    }
  }
}

Try it against the demo app:

1. launch_app with java -jar swing-mcp-demo/target/swing-mcp-demo-1.0.0.jar
2. take_snapshot to discover component UIDs
3. click, fill, select_option, … to interact

MCP Registry

This server is published to the MCP Registry as io.github.TinusJ/swing-mcp, distributed as an MCPB bundle attached to GitHub releases. See docs/registry-publishing.md for how publishing works.

Security notes

• The agent listens on the loopback interface only.
• evaluate_java (arbitrary code execution in the target JVM) is disabled by default; enable with swing.mcp.evaluate.enabled=true.