How to use instance metadata from within Cloudwatch agent config

I would like to add a dimension to several metrics using "append_dimensions" into Cloudwatch agent config. As specified here, it says "If you specify a value that depends on Amazon EC2 metadata". How do I specify a value, of a specific instance tags from instance metadata, for example? Is it "append_dimensions": { "Environment": <how to reach an instance tag called Environment> }?