analyze_class
Analyze structure, methods, fields and other information of a Java class
LABSCO SUMMARY
An agent that cannot see inside a JAR will invent what is inside it.
Small surface, one job. scan_dependencies makes the project's classes addressable, decompile_class gives back real source, analyze_class gives the shape when full source is more than you need. If you have watched an assistant confidently describe a framework method that does not exist, this is the fix for that exact failure.
What it is
An MCP server that indexes a Maven or Gradle project's dependencies and decompiles classes out of the JARs. The decompiler ships with the package, so there is nothing to install alongside it.
What you get
- scan_dependencies — walk the project's dependencies and build an index from class name to the JAR that holds it
- decompile_class — the full Java source for any class in that index
- analyze_class — the structure: methods, fields, inheritance and other declared members
- The index is built on demand if it is missing, and results are cached after the first decompile
Requirements
Node, and a Java project whose dependencies are already resolved locally — the server reads the build files and the local repository. No decompiler to install; it is bundled with the package.
Setup effort
One command — npx -y jarp-mcp
USE CASES
01
Asking how a framework method actually works
Index the project's dependencies, then read the decompiled source of the class instead of a plausible guess.
02
Checking a signature before calling it
Pull the class's methods and fields without decompiling the whole file.
03
Debugging an exception thrown inside a library
Decompile the class named in the stack trace and read the branch that threw.
3 tools
Counted once with only startup setup. Other versions, modes or optional credentials may expose a different list.
decompile_class
Decompile specified Java class file and return Java source code
scan_dependencies
Scan all dependencies of a Maven project and build mapping index from class names to JAR packages
BEFORE YOU INSTALL
What to know first
Tools you get
3 tools when we connected.
Requires
npx on PATH
CONTEXT COST
Light Standing cost
Rated by the size of the 3 tool definitions that ride along on every turn, not by how many there are
INSTALLATION
Connect your client
Add the block to your client, or run the command directly.
Server setup
Configuration file
JSON
{
"mcpServers": {
"jarp-mcp": {
"command": "npx",
"args": [
"-y",
"jarp-mcp"
]
}
}
}npx
TERMINAL
npx -y jarp-mcp
