update tools docs

docs/src/tools.md

@@ -1,15 +1,30 @@
 # Tools
 
-
 ## Entanglement Entropy
-What it is? What it tells us...
+
+### Overview
+
 ### Bipartite Entanglement Entropy (BEE)
+Given a [`trainedMPS`](@ref), we can compute the bipartite entanglement entropy (BEE) using:
+```Julia
+bees = bipartite_spectrum(mps);
+``` 
+The return value is a vector corresponding to the BEE of each class mps.
 
 
 ### Single-Site Entanglement Entropy (SEE)
+Given a [`trainedMPS`](@ref), we can compute the single-site entanglement entropy (SEE) using:
+```Julia
+sees = MPSTime.single_site_spectrum(mps);
+``` 
 
+## Docstrings
 ```@docs
 MPSTime.von_neumann_entropy
 MPSTime.bipartite_spectrum
+```
+
+## Internal Methods
+```@docs
 MPSTime.single_site_spectrum
 ```