[Kiro Setup] How to Fix "Failed to connect to MCP server" Error when configuring MCP (Part 1)

Introduction: Troubleshooting MCP Errors in Kiro

Hello! This is Matsuura from the DX Solution Sales Division.

When attempting to configure MCP (Model Context Protocol) in Kiro, you might encounter specific errors.
In this article, we will focus on the "Failed to connect to MCP server" error, explaining its cause and providing step-by-step instructions to fix it.

1. Environment

The information in this article is based on the following environment:

• OS: Windows 11
• Python: Python 3.9.6 or later installed
• Kiro: 0.8.140 (latest version at the time of writing)

2. Error Details

When setting up the "AWS Documentation MCP Server" in Kiro, the following error message appeared:

Failed to connect to MCP server "awslabs.aws-documentation-mcp-server": MCP error -32000: Connection closed

This error occurred while following the MCP configuration steps described in the article below:

3. Root Cause

The cause of this error was that the uv package was not installed.

In Kiro's MCP configuration, many MCP servers are executed using the uvx command. uvx is a command included in the Python package manager "uv." If this is not installed, the connection to the MCP server will fail.

What is uv?

uv is an extremely fast Python package manager written in Rust. Compared to traditional tools like pip or pipenv, it offers:

• Fast package installation
• Efficient dependency resolution
• Direct execution of packages via the uvx command

4. Solution

Follow these steps to install uv and configure your environment variables.

Step 1: Install uv via PowerShell

Open PowerShell as an Administrator and run the following command:

powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"

This command downloads and runs the official uv installation script.

Step 2: Add to Environment Variables (Path)

Add uv to your Path so the command can be executed from anywhere.

2-1. Open System Properties

1. Press Windows Key + R, type sysdm.cpl, and hit Enter.
2. Click the "Advanced" tab.
3. Click "Environment Variables."

2-2. Edit Path Variable

1. Select "Path" under User or System variables.
2. Click "Edit," then "New."
3. Add the following path (replace [Username] with your actual Windows username):

C:\Users\[Username]\.local\bin

→ Click "OK" to save the settings.

Step 3: Restart PowerShell

Close all open PowerShell windows and open a new one to apply the environment variable changes.

Step 4: Verify uv Installation

In the new PowerShell window, run the following command to confirm installation:

uv --version

If the version information appears, the installation was successful.

5. Verification

Once uv is installed, try connecting to the MCP in Kiro again.

Step 1: Restart Kiro

Completely exit Kiro and launch it again. This ensures the new environment variables are recognized.

Step 2: Check MCP Connection

Check the connection status in Kiro's settings or the MCP Server view. If successfully connected, the error will disappear.

Step 3: Test with MCP Tools

Try searching the AWS Documentation using the MCP tool. If it works as expected, your configuration is complete!

Summary: Resolving MCP Connections by Installing uv

If you encounter the "Failed to connect to MCP server" error in Kiro, a missing "uv" package is a likely culprit.

Follow these steps to resolve it:

1. Install uv via PowerShell
2. Add the uv path to your Environment Variables
3. Restart both PowerShell and Kiro
4. Verify the MCP connection

With this fix, you can fully leverage MCP servers in Kiro. Referencing external resources like official AWS documentation directly within Kiro will significantly boost your development efficiency. Give it a try!

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