expression, noun which may take the genitive case particle 'no'
just right; ideal; perfectly suitable
Describes something that is exactly what is needed or perfectly suited for a purpose. Often used in the pattern ～にもってこい.
この仕事は彼にもってこいだ。
This job is just right for him.
この本は日本語の勉強にもってこいです。
This book is ideal for studying Japanese.
expression
fetch!; bring me ...
Imperative form of 持ってくる (to bring). Used as a command or request to bring something. This sense is a literal verb phrase, not the idiomatic 'just right' meaning.
犬に「持ってこい」と言った。
I told the dog, "Fetch!"
その本を持ってこい。
Bring me that book.