How to configure environment variables such as BING_SEARCH_URL and SEARCH_TOOL_API_URL

Hi, thanks for your great work on this project!

I’m currently running into an issue where some environment variables (e.g., BING_SEARCH_URL and SEARCH_TOOL_API_URL) are not set by default. I couldn’t find clear documentation on how or where to define them.

Could you please clarify:

1. The expected values or formats for these environment variables;
2. Whether there’s a recommended way to configure them globally;
3. If there are any sample environment files or configuration examples available.

Thanks in advance for your help!