AssistAI - Eclipse IDE as an MCP Server for AI Agents

AssistAI is an Eclipse IDE plugin that exposes your entire development environment as an MCP (Model Context Protocol) server. External AI agents -- Claude Code, OpenAI Codex, Claude Desktop, or any MCP-compatible client -- can read, navigate, edit, build, test, run, and debug your Java projects directly through Eclipse, preserving workspace sync, local history, and incremental compilation.

AssistAI also includes a built-in LLM chat view for quick inline interactions with any supported model.

Why MCP through Eclipse?

When AI agents edit files through the filesystem directly, Eclipse doesn't know anything changed. Editors show stale content, incremental compilation misses updates, and local history gaps appear.

AssistAI solves this by routing all operations through Eclipse APIs:

• Edits go through JDT -- incremental compilation fires immediately, errors update in real time
• Refactorings use Eclipse's refactoring engine -- renames, moves, and package restructures update all references across the workspace
• File reads reflect the editor buffer -- agents always see the latest unsaved content, not the on-disk version
• Local history is preserved -- every change is tracked, undoable through Eclipse's local history
• Tests run inside Eclipse -- JUnit results, console output, and compilation errors are accessible as tool responses

Getting Started with External Agents

1. Enable the HTTP MCP Server

1. Open Window > Preferences > Assist AI > HTTP MCP Server
2. Check Enable HTTP MCP Server
3. Set Hostname and Port (defaults: localhost:8124)
4. Click Generate to create an authentication token
5. Click Apply -- the server starts immediately

The status panel shows all available endpoints:

• http://localhost:8124/mcp/eclipse-ide -- code analysis, navigation, search, testing, builds
• http://localhost:8124/mcp/eclipse-coder -- file editing, refactoring, patching, formatting
• http://localhost:8124/mcp/eclipse-runner -- launch, debug, breakpoints, stepping
• http://localhost:8124/mcp/eclipse-context -- resource cache, file local history, version tracking
• http://localhost:8124/mcp/eclipse-git -- git status, log, staging, commit, diff, branches, stash

2. Connect Your Agent

Claude Code

Add to your Claude Code MCP settings (.claude/settings.json or project-level(.mcp.json in project root)):

{
  "mcpServers": {
    "eclipse-ide": {
      "command": "npx",
      "args": [
        "-y", "mcp-remote", "http://localhost:8124/mcp/eclipse-ide",
        "--allow-http",
        "--header", "Authorization: Bearer YOUR_TOKEN"
      ]
    },
    "eclipse-coder": {
      "command": "npx",
      "args": [
        "-y", "mcp-remote", "http://localhost:8124/mcp/eclipse-coder",
        "--allow-http",
        "--header", "Authorization: Bearer YOUR_TOKEN"
      ]
    },
    "eclipse-runner": {
      "command": "npx",
      "args": [
        "-y", "mcp-remote", "http://localhost:8124/mcp/eclipse-runner",
        "--allow-http",
        "--header", "Authorization: Bearer YOUR_TOKEN"
      ]
    },
    "eclipse-git": {
      "command": "npx",
      "args": [
        "-y", "mcp-remote", "http://localhost:8124/mcp/eclipse-git",
        "--allow-http",
        "--header", "Authorization: Bearer YOUR_TOKEN"
      ]
    }
  }
}

On Windows with WSL, use "command": "wsl" and prepend "npx" to the args array.

Claude Desktop

Add to your Claude Desktop configuration file:

• Windows: %APPDATA%\Roaming\Claude\claude_desktop_config.json
• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Linux: ~/.config/Claude/claude_desktop_config.json

Use the same mcpServers format as above.

OpenAI Codex / Other MCP Clients

Any client that supports MCP over Streamable HTTP can connect directly to the endpoint URLs. Use the Authorization: Bearer <token> header for authentication.

3. What Agents Can Do

With the MCP tools, an external agent can:

• Read and navigate code -- project layout, class outlines, method source, type hierarchies, call hierarchies, find references
• Edit code -- create files, apply unified diffs, replace strings, delete lines, replace entire files
• Refactor -- rename types/packages, move types, organize imports -- all through Eclipse's refactoring engine
• Build and test -- run Maven builds, execute JUnit tests (all, by package, class, or method), read compilation errors, get quick-fix suggestions
• Search -- text search, regex search, file glob search, search-and-replace across the workspace
• Run and debug -- launch Java applications, set breakpoints (including conditional), step through code, inspect stack traces, evaluate expressions, hot-swap code
• Access context -- read JavaDoc, console output, editor selection, effective POM, project dependencies
• Browse and restore file history -- list Local History versions, view old content, restore to any previous version, diff current vs. historical
• Inspect the resource cache -- see what files/classes are loaded in the conversation context, read cached content without I/O
• Manage Git repositories -- status, log, diff, stage, commit, branch, checkout, stash -- all through EGit, keeping Eclipse workspace in sync
• Navigate large documents -- get the heading outline of a Markdown file, then fetch specific sections without loading the entire content

4. Guiding Agents with Eclipse Context

External agents don't know what you're looking at in Eclipse -- unless they ask. AssistAI provides MCP tools that let agents pick up context from your IDE session, so you can guide their work by simply opening files, selecting code, or running programs:

Workflow tip: When asking an agent to fix something, open the relevant file in Eclipse first, select the problem area, and tell the agent to check your selection. This gives the agent precise context without you having to describe file paths or paste code.

Token-efficient navigation: Instead of reading entire files, agents can use getClassOutline to see the structure (~30 lines for a 500-line class), then getMethodSource to read only the methods they need, or getFilteredSource to see the full file with irrelevant methods collapsed to one-line signatures. The readProjectResource tool supports excludeImports to further reduce token usage.

Resource cache: Files and classes read through Eclipse MCP tools are automatically cached with version tracking and file modification timestamps (tied to Eclipse's Local History). Agents can call listCachedResources to see what's already loaded, or getCachedResource to re-read cached content instantly -- no disk I/O, no re-parsing.

Local History: Eclipse automatically maintains a Local History for every file modified through the IDE. Agents can browse past versions (getFileHistory), read historical content (getFileHistoryContent), compare with the current version (compareWithHistory), or restore to any previous state (restoreFileVersion). This is more powerful than a simple undo -- it preserves every edit across the entire session, including changes made by the agent itself.

MCP Tool Reference

eclipse-coder -- Code Editing

eclipse-ide -- Code Analysis, Navigation & Build