Descartes Java REPL and Deep Introspection For Your Java Apps

@Wido Riezebos

4 months ago

A Java-based Model Context Protocol (MCP) server that provides deep introspection, monitoring, debugging, and REPL capabilities for Java applications. Descartes enables AI assistants to interact with running Java processes through a comprehensive set of tools and resources. Kind of does for the Java backend what Playwright does for the frontend. Easy to add as a maven dependency to your Java application.

Overview Tools Comments

Overview

Descartes MCP

⚠️ SECURITY WARNING: This tool includes a Java REPL that allows arbitrary code execution. It should ONLY be used in development/debugging environments and NEVER exposed to untrusted networks or users.

Features

🛠️ Tools

JShell REPL: Interactive Java code execution with session management
Object Inspector: Deep object introspection without code execution
Process Inspector: Process and thread information monitoring
System Monitoring: Real-time system metrics and resource usage
Thread Analyzer: Thread state analysis and deadlock detection
Memory Analyzer: Heap usage, garbage collection, and memory pool analysis
Exception Analysis: Stack trace analysis and root cause identification
Logging Integration: Log4j2 integration for log capture and analysis

📊 Resources

Classpath Resource: Access to classpath information
System Properties: JVM and system property access
Metrics Resource: Application and JVM metrics
Thread Dumps: Detailed thread state snapshots
MBean Resource: JMX MBean access and monitoring
Application Context: Access to registered application objects

Session Management

The JShell integration provides sophisticated session management:

Isolated Execution Contexts: Each AI conversation gets its own JShell instance with separate variable namespaces, preventing cross-contamination between sessions.
Configurable Timeouts: Sessions automatically expire after inactivity (default: 30 minutes) to prevent memory leaks.
State Preservation: Variables and imports persist across multiple evaluations within the same session, enabling complex multi-step interactions.
Context Injection: Application objects from the context map can be automatically exposed to JShell sessions, allowing direct manipulation of live application state.
Concurrent Session Support: Multiple sessions can run simultaneously without interference.

Try in Playground

Server Config

{
  "mcpServers": {
    "morpheus": {
      "command": "node",
      "args": [
        "/path/to/mcp/mcp-tcp-adapter.js"
      ],
      "env": {
        "MCP_HOST": "localhost",
        "MCP_PORT": "9080",
        "MCP_DEBUG": "false",
        "MCP_RECONNECT_MIN_DELAY": "500",
        "MCP_RECONNECT_MAX_DELAY": "5000",
        "MCP_HEALTH_CHECK_INTERVAL": "5000",
        "MCP_LOG_RATE_LIMIT_WINDOW": "60000",
        "MCP_LOG_RATE_LIMIT_MAX": "10"
      }
    }
  }
}

Build with ShipAny.