We fix a path model for the space of filters of the inverse semigroup S Λ associated to a left cancellative small category Λ. Then, we compute its tight groupoid, thus giving a representation of its C * -algebra as a (full) groupoid algebra. Using it, we characterize when these algebras are simple. Also, we determine amenability of the tight groupoid under mild, reasonable hypotheses. 2010 Mathematics Subject Classification. Primary: 46L05; Secondary: 46L80, 46L55, 20L05. . α ∨ β := {the minimal extensions of α and β} .Notice that if α ∨ β = ∅ then α ⋓ β, but the converse fails in general.When Λ is a finitely aligned LCSC, we can always assume that α ∨ β = Γ where Γ is a finite set of minimal common extensions of α and β. 1.2. Inverse semigroups. Definition 1.9. A semigroup S is an inverse semigroup if for every s ∈ S there exists a unique s * ∈ S such that s = ss * s and s * = s * ss * . Equivalently, S is an inverse semigroup if and only if the subsemigroup E(S) := {e ∈ S : e 2 = e} of idempotents of S is commutative [12, Theorem 1.1.3].A monoid is a semigroup with unit. We say that a semigroup S has zero if there exists 0 ∈ S such that 0s = s0 = 0 for every s ∈ S.Definition 1.10. Given a set X, we define the (symmetric) inverse semigroup on X as