It's "pajamas are". Because this word is always used in a plural form, it's incorrect to say "pajamas is".
It's "pajamas are". Because this noun is always used in the plural, it's incorrect to say "pajamas is".
My pajamas are soft and loose.
My pajamas is soft and loose.
However, the phrase "a pair of pajamas" requires a singular verb.
There is a pair of pajamas in the drawer. (not "There are...")
Follow the same convention with other verbs, such as fit, have, include, look, etc.
Your new pajamas look appropriate for daytime. (not "looks appropriate")
Be aware that we always use a plural determiner or pronoun (these, those, them, they, etc.) with plural nouns, like "pajamas".
Those pajamas fit perfectly. Do you like them?
A partial list of clothing-related nouns that only have a plural form, and therefore take "are":