What's the adjective for sheathless? Here's the word you're looking for.
Included below are past participle and present participle forms for the
verbs sheath and sheathe which may be used as adjectives within certain contexts.
sheathable
(rare) Capable of being sheathed. (usually a bladed weapon of some kind)
“Wearing only an open, sheathlike black cloak, the actress holds an extravagantly long chain of flowers that trails awkwardly alongside her.”
“It features a prominent partial veil which covers the young gills and later forms a sheathlike covering on the lower stem, with the upper edge flaring outward to form a ring.”