Is the JShell REPL safe to use in production?
No. The REPL allows arbitrary code execution with full JVM permissions. It should only be used in development/debugging environments and never exposed to untrusted networks or users.

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Basic information
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.
Add this server to your MCP-compatible client using the configuration below.
{
"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"
}
}
}
}Tool list not available yet
This listing does not currently have a tool list to display. This does not mean the server has no tools; check its documentation for supported capabilities.
We auto-extract tools from the README. The maintainer can list them under a ## Tools heading to populate this section.
Descartes Java REPL and Deep Introspection For Your Java Apps is a Java‑based Model Context Protocol (MCP) server that provides deep introspection, monitoring, debugging, and a JShell REPL for Java applications. It enables AI assistants to interact with running Java processes through a comprehensive set of tools and resources.
Clone the repository, build with mvn clean package, and run the example server with mvn exec:java. Connect an MCP client via the included TCP adapter (config/mcp/mcp-tcp-adapter.js) and configure it in your client’s JSON configuration. The server listens on port 9080 by default.
No. The REPL allows arbitrary code execution with full JVM permissions. It should only be used in development/debugging environments and never exposed to untrusted networks or users.
Java 16 or higher (compiled with Java 23), Maven 3.6+, and Node.js for the TCP adapter.
All introspection data and REPL sessions live inside the target JVM process. Application objects are accessible via a context map; resources provide read‑only views of system state.
The server uses JSON‑RPC 2.0 over TCP sockets. Each client connection runs in a separate thread for concurrent operation.
The README recommends restricting access to localhost only, and warns against exposing the server beyond trusted networks. No built‑in authentication layers are described.
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