Yes, HAGGADAS is a Scrabble word!

Letter values in Scrabble US: H 4, A 1, G 2, G 2, A 1, D 2, A 1, S 1.

Is it a valid word?

HAGGADAS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

Talmudic literature that does not deal with law but is still part of Jewish tradition
Talmudic literature that does not deal with law but is still part of Jewish tradition

Not playable in Scrabble US: HAGADA.