diff --git a/README.md b/README.md
index 37025cc..b57e153 100644
--- a/README.md
+++ b/README.md
@@ -15,7 +15,7 @@ The package is registered in the General registry, and can be installed from the
 
 ## Usage
 
-The `assign_secondary_structure` function takes a vector of atom coordinate arrays of size (3, 3, L). The first axis is for the x, y, and z coordinates, the second axis is for the atom types (N, CA, C), and the third axis is for the residues.
+The `assign_secondary_structure` function takes a vector of atom coordinate arrays of size `(3, 3, L)`. The first axis is for the x, y, and z coordinates, the second axis is for the atom types (N, CA, C), and the third axis is for the residues.
 
 ```julia
 julia> using BioStructures
@@ -32,6 +32,11 @@ julia> assign_secondary_structure(coords_vector) # 2 chains
  [1, 1, 1, 1, 3, 3, 3, 3, 3, 3  …  2, 2, 2, 2, 2, 2, 2, 1, 1, 1]
 ```
 
+The output is vectors of integers:
+- `1`: loop
+- `2`: helix
+- `3`: strand
+
 ## Acknowledgements
 
 This package was originally ported from the [PyDSSP](https://github.com/ShintaroMinami/PyDSSP) package, created by Shintaro Minami. The code has since been rewritten to look more like the 1983 paper (Kabsch W and Sander C), and to be more Julian, understandable, and efficient, at the cost of it no longer being differentiable like the PyDSSP version. The time complexity is still quadratic, so it may be slow for larger proteins. We plan on making a more efficient version with k-d trees.