diff --git a/src/certificate_store.rs b/src/certificate_store.rs
index c258680..8123279 100644
--- a/src/certificate_store.rs
+++ b/src/certificate_store.rs
@@ -1,9 +1,14 @@
 use std::collections::{BTreeMap, HashMap};
 
-/// An item which stores known certificates
+/// An item which stores known certificates. For convenience, this trait is implemented for
+/// `std::collections::HashMap<String, String>` and `std::collections::BTreeMap<String, String>`
 pub trait CertificateStore: Send + Sync {
+    /// Retrieves a certificate fingerprint using the hostname as it's key if 
+    /// it has previously been saved
     fn get_certificate(&self, host: &str) -> Option<String>;
+    /// Inserts a certificate fingerprint with the hostname as the key
     fn insert_certificate(&mut self, host: &str, fingerprint: &str) -> Option<String>;
+    /// Returns true if a fingerprint has been stored for this host
     fn contains_certificate(&self, host: &str) -> bool;
 }