MCP Inspector & Debugger – Castov (VS Code Extension)

Inspect, debug, test, audit, and log Model Context Protocol (MCP) servers directly inside Visual Studio Code and Cursor IDE.

No external web browsers needed, zero bloat, native STDIO JSON-RPC 2.0 communication.

✨ Features

Automatically detects servers defined in:
- .cursor/mcp.json
- .vscode/mcp.json
- Local workspace mcp.json
- Claude Desktop config (claude_desktop_config.json on Windows, macOS, Linux)
Live file watcher automatically reloads server lists when configuration files change.

Dynamic UI generated automatically from the tool's JSON Schema (inputSchema.properties).
Supports booleans, numbers, strings, and JSON objects/arrays.
One-click tool execution (tools/call) over STDIO JSON-RPC 2.0 with formatted JSON responses and real-time execution latency (⏱️ 35ms).

View raw JSON-RPC 2.0 messages passing between VS Code and the server in real-time.
Tracks method names, timestamps, execution latency, and full request/response payloads.

Exposed Secret Detection: Catches hardcoded API keys in plain text args or env (OpenAI sk-..., Anthropic sk-ant-..., GitHub ghp_..., AWS keys).
Dangerous System Privileges: Flags unrestricted shells (bash, cmd.exe, powershell), sudo elevation, and remote script pipes (curl | sh).
Prompt Injection Defense: Scans tool descriptions for jailbreak and system hijacking patterns (e.g. "Ignore previous instructions", "SYSTEM PROMPT:").

Command	Description
`MCP: Open Interactive Inspector & Tester`	Opens the full-featured Webview Playground
`MCP: Refresh & Discover Servers`	Rescans workspace and global paths for MCP servers
`MCP: Run Security Audit on Configs`	Audits server configs and tool definitions for vulnerabilities
`MCP: Test Selected Tool`	Jumps directly to testing a specific tool from the sidebar

Install mcp-inspector in VS Code or Cursor.
Open any workspace with a .cursor/mcp.json or .vscode/mcp.json.
Click the MCP Inspector icon in the Activity Bar or press Ctrl+Shift+P -> MCP: Open Interactive Inspector & Tester.
Select your server, pick a tool, fill in test parameters, and press Execute Tool!