FIRECRAWL_API_KEY Id is not getting value from .env file

Question

I was following the Advent of Agent and was building the multi-agent app with Firecrawl.

When I am using this line FIRECRAWL_API_KEY: "${FIRECRAWL_API_KEY}" inside the research_agent.yaml and the actual value inside the .env file, it is giving me below error "The research agent encountered an "Unauthorized: Invalid token" error when attempting to access the site." But when I am putting the same key inside the research_agent.yaml file, it is working fine. I don't think we are supposed to expose the key inside the yaml file, rather it should get the value from .env file.

Any idea what can be the reason for this error?

Here is the Github Code: https://github.com/suddeb/Advent-of-Agents/tree/main/multi_agent