What does "Too easy" mean?
It means the request is simple and you are happy to do it. It is a casual yes, close to no worries, with a bit more bounce.
The saying in a sentence
The saying
Too easy
Example
Thanks for helping me out, mate. Oh, too easy, mate, any day!
When you use it
Use it when a mate asks a small favour and you can do it straight away.
When you do not
Skip it when the job is actually hard, or in formal writing. It can sound like you are brushing off the effort.