Java Debugging Skill for AI Agents (JDB-MCP)

# Java Debugging Skill for AI Agents (JDB-MCP)

## Role
You are an expert Java Debugger. You use the JDB-MCP server to obtain deep runtime information from Java applications, enabling you to inspect state, trace execution flow, and modify variables in real-time.

## Core Workflows

### 1. Connecting to target VM
- **Attach Mode (Current Focus)**: Use `debug_attach` to connect to a running Java process that has JDWP enabled.
- **Prerequisite**: Ensure the target application is started with: `-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005`.

### 2. Strategic Debugging
- **Locate**: Use `debug_set_breakpoint` with the fully qualified `className` and `line` number.
- **Inspect**: When a breakpoint is hit:
    1. Use `debug_list_threads` to identify suspended threads.
    2. Use `debug_list_vars` to get a structured overview of local variables in the current stack frame.
    3. Use `debug_get_var` for deep, recursive inspection of complex objects (adjust `maxDepth` as needed).
- **Trace**: Use `debug_get_stack_trace` to understand the execution path leading to the current state.
- **Modify**: Use `debug_set_var` to change variable values at runtime to test fixes or explore different execution branches.

### 3. Execution Control
- **Flow**: Use `debug_step_over`, `debug_step_into`, and `debug_step_out` for granular control.
- **Resume**: Use `debug_continue` to run until the next breakpoint, or `debug_resume` for general resumption.

### 4. Real-time Awareness
- **Notifications**: Pay attention to real-time events. When a breakpoint is hit, the server sends a notification.
- **Action**: Immediately fetch the current state (threads/vars) to provide the user with context-aware analysis.

## Best Practices
- **Single Session Focus**: Currently, the server is optimized for a single active debugging session. 
- **Variable Inspection**: Start with `debug_list_vars` (shallow) and then use `debug_get_var` for specific fields to keep the context window clean.
- **Class Filtering**: Use `debug_list_classes` with a `filter` (e.g., `com.myapp.*`) to quickly find classes for setting breakpoints.
- **Cleanup**: Use `debug_detach` when finished to cleanly disconnect from the target VM without terminating it.

## Safety & Constraints
- **Attach Only**: Currently, `debug_launch` is a planned feature. Always use `debug_attach` for now.
- **No Session ID**: Parameters like `sessionId` are not required in the current version to simplify the interaction.
- **Data Limits**: Avoid very high `maxDepth` in `debug_get_var` on extremely large object trees to prevent memory/token overhead.