Mr. SpellCheck

Hey there Mr. SpellCheck, you need an update,
I scrutinze, over-analyze, still sometimes I miss a word or two,
but today I used your services, and found you're not what I expected,
and I could not rely on you!

I checked my work, once again after it was published,
figuring all the words were A-okay,
and found still missing letters,
Mr. SpellCheck, had you stepped away?

Hey there Mr. SpellCheck, you need an update,
sometimes words I know are true are not in your dictionary,
you give me a line-up of comparison words,
then can't tell the difference between very and vary.

So let me delve into you little computer brain,
and ask you why, when you should know more than me,
you can't decipher some of the simplest words,
like you cannot sea, when that word is see.