diff --git a/src/bcrypt.rs b/src/bcrypt.rs
index 9f0b16e..1d9443f 100644
--- a/src/bcrypt.rs
+++ b/src/bcrypt.rs
@@ -13,6 +13,10 @@ fn setup(cost: u32, salt: &[u8], key: &[u8]) -> Blowfish {
     state
 }
 
+/// The bcrypt key derivation function.
+///
+/// - `cost` must be between 4 and 31.
+/// - The length of `password` must be between 1 and 72.
 pub fn bcrypt(cost: u32, salt: [u8; 16], password: &[u8]) -> [u8; 24] {
     assert!(!password.is_empty() && password.len() <= 72);
 
diff --git a/src/lib.rs b/src/lib.rs
index 9488a8c..a80e72f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,4 +1,5 @@
 //! Easily hash and verify passwords using bcrypt
+#![deny(missing_docs)]
 #![forbid(unsafe_code)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
@@ -25,7 +26,9 @@ pub use crate::errors::{BcryptError, BcryptResult};
 // Cost constants
 const MIN_COST: u32 = 4;
 const MAX_COST: u32 = 31;
+/// The default cost parameter.
 pub const DEFAULT_COST: u32 = 12;
+/// Base64 variant used by bcrypt.
 pub const BASE_64: GeneralPurpose = GeneralPurpose::new(&BCRYPT, NO_PAD);
 
 #[cfg(any(feature = "alloc", feature = "std"))]
@@ -41,9 +44,13 @@ pub struct HashParts {
 /// BCrypt hash version
 /// https://en.wikipedia.org/wiki/Bcrypt#Versioning_history
 pub enum Version {
+    /// Version `$2a$`.
     TwoA,
+    /// Version `$2x$`.
     TwoX,
+    /// Version `$2y$`.
     TwoY,
+    /// Version `$2b$`.
     TwoB,
 }