Updated readme

Author: DevonFulcher

examples/langgraph_agent/README.md

@@ -4,4 +4,5 @@ This is a simple example of how to create conversational agent with remote dbt M
 
 ## Usage
 
-Run `uv run main.py`.
+1. Set an `ANTHROPIC_API_KEY` environment variable with your Anthropic API key.
+2. Run `uv run main.py`.