grammar - What (if any) is the proper hyphenation for the phrase "it's all too easy"?

Are any of the following correct?

It's all too-easy
It's all-too-easy
It's all too easy

Explanation/citations would be greatly appreciated

Answer

There is no need to hyphenate the phrase unless it is used either as a compound noun or as a compound adjective.

As a compound noun, it is likely to be a nickname, in which case, capitalise the initial letters:

• 
  It's All-Too-Easy (as in names such as John-Paul, or Maria-Luisa)


• It's 'All Too Easy' (as a nickname) and It's All Too Easy (as a non-hyphenated name) would both also be acceptable.

As a compound adjective, it would need a determiner before it, e.g.,

• It's the all-too-easy solution to all our problems. Don't you believe it.

ADDITION:

In the plural, eg 'all-too-easy solutions' no determiner is needed, as Kris commented, below.