MCP Inspector

MCP

MCPGitHubLevel: IntermediateFree

MCP Inspector

4.0/52dm rating

A tool worth having when trying out and debugging servers.

A UI tool for trying out and debugging MCP servers before attaching them to an AI assistant.

Official site How to use it

Overview

MCP Inspector is a developer tool for testing and debugging MCP servers. You connect Inspector to a server, view its list of tools, resources and prompts, and try calling each tool to make sure the server works correctly before handing it to users.

Everything is in a single @modelcontextprotocol/inspector package with several modes: a web interface (default), a CLI for scripting and running in CI, a TUI terminal interface, and the experimental mcpdo for running multiple commands over a named connection.

Inspector manages OAuth tokens, client secrets and the server's environment variables; by default it stores them in the operating system keychain if available, and on machines without a keychain it stores them in an unencrypted file unless you provide a key.

Highlights

Visual tool calling

The web interface lets you view and try the server's tools, resources and prompts.

Multiple modes

Web, CLI, TUI and experimental mcpdo in the same package.

Fits automation

CLI mode works in scripts, CI and agent loops.

Runs without installation

Launch directly via npx.

Secrets stored in the keychain

OAuth tokens and secrets are stored in the operating system keychain by default when available.

What it's for

Checking a server before handover

The IT team tries each tool to confirm the internal server returns correct results.

Debugging connections

Determine whether the fault is in the server or the AI app when the assistant cannot call a tool.

Automated testing

Add CLI mode to the CI pipeline to catch bugs each time the server is updated.

Evaluating third-party servers

See which tools a public server exposes before allowing its use in the company.

How to use it

1
Open the web interface
Run Inspector in default mode to connect to and try a server.
$npx @modelcontextprotocol/inspector
2
Use CLI mode
Use it when you need to run checks by script or in CI.
$npx @modelcontextprotocol/inspector --cli
3
Use TUI mode
An interface right in the terminal for people comfortable with the command line.
$npx @modelcontextprotocol/inspector --tui
4
Configure the server to connect
Declare the server following the MCP server configuration guide in the repo's documentation.
5
Call and read results
Select each tool, enter sample parameters and check the response before real use.

Video guides

10 - MCP Inspector: Test and Debug your MCP Server Locally
AI Anytime

Build & Test a MCP Server with TypeScript and MCP Inspector
Roy Derks

How to test MCP server using MCP Inspector
Jaydeep Karale

Real-world example

Illustrative scenario

A logistics company in Binh Duong has just written an MCP server for looking up shipment status. Before letting customer care staff use it, a developer opens Inspector, calls the shipment lookup tool with a few sample codes and checks the error message when a wrong code is entered. They then add the Inspector CLI command to the CI process to re-check every time the server is changed.

Tips & notes

Check where secrets are stored
On servers without a keychain, secrets sit in an unencrypted file; provide a key or restrict access.
Use test data
Call tools with sample data to avoid accidentally changing real data.
Automate with the CLI
Put CLI mode in CI so you do not have to test manually after every update.
Need a recent enough Node for development
To build from source, the README requires Node 22.19.0 or higher.