Prerequisites

• I've searched the current open issues
• I've updated to the latest version of Toolbox

Toolbox version

toolbox version 0.17.0+binary.linux.amd64.de19d52

Environment

1. Linux 6.14.0-33-generic #33-Ubuntu SMP PREEMPT_DYNAMIC Wed Sep 17 23:22:02 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
2. How are you running Toolbox:

• from curl -O https://storage.googleapis.com/genai-toolbox/v0.17.0/linux/amd64/toolbox

Client

1. Client: claude code
2. Version: 2.0.14 (Claude Code)
3. Example: If possible, please include your code of configuration:

{
  "mcpServers": {
    "mysql": {
      "command": "./PATH/TO/toolbox",
      "args": ["--prebuilt", "mysql", "--stdio"],
      "env": {
        "MYSQL_HOST": "",
        "MYSQL_PORT": "",
        "MYSQL_DATABASE": "",
        "MYSQL_USER": "",
        "MYSQL_PASSWORD": ""
      }
    }
  }
}

Expected Behavior

The MCP server should start normally for Claude Code to call.

Current Behavior

Claude Code is unable to start the MCP server. Attempting to reproduce the issue using the same command and environment variables results in the following error message:

2025-10-11T14:19:06.254553107+08:00 INFO "Using prebuilt tool configuration for mysql" 
2025-10-11T14:19:06.25607058+08:00 ERROR "toolbox failed to initialize: unable to initialize configs: unable to initialize source \"mysql-source\": unable to create pool: sql.Open: invalid DSN: did you forget to escape a param value?" 

Steps to reproduce?

Please refer to: https://googleapis.github.io/genai-toolbox/dev/how-to/connect-ide/mysql_mcp/

Additional Details

This issue might be related to #1617