diff --git a/src/crypto.rs b/src/crypto.rs
index cd141ed..b5415a8 100644
--- a/src/crypto.rs
+++ b/src/crypto.rs
@@ -17,12 +17,18 @@ use validation::{Validation, validate};
 /// The algorithms supported for signing/verifying
 #[derive(Debug, PartialEq, Copy, Clone, Serialize, Deserialize)]
 pub enum Algorithm {
+    /// HMAC using SHA-256
     HS256,
+    /// HMAC using SHA-384
     HS384,
+    /// HMAC using SHA-512
     HS512,
 
+    /// RSASSA-PKCS1-v1_5 using SHA-256
     RS256,
+    /// RSASSA-PKCS1-v1_5 using SHA-384
     RS384,
+    /// RSASSA-PKCS1-v1_5 using SHA-512
     RS512,
 }
 
@@ -72,7 +78,7 @@ pub fn sign(signing_input: &str, key: &[u8], algorithm: Algorithm) -> Result<Str
     }
 }
 
-/// Encode the claims passed and sign the payload using the algorithm from the header and the key
+/// Encode the header and claims given and sign the payload using the algorithm from the header and the key
 pub fn encode<T: Serialize>(header: &Header, claims: &T, key: &[u8]) -> Result<String> {
     let encoded_header = to_jwt_part(&header)?;
     let encoded_claims = to_jwt_part(&claims)?;
@@ -82,10 +88,11 @@ pub fn encode<T: Serialize>(header: &Header, claims: &T, key: &[u8]) -> Result<S
     Ok([signing_input, signature].join("."))
 }
 
-/// Compares the signature given with a re-computed signature for HMAC or using the public key (`key`)
+/// Compares the signature given with a re-computed signature for HMAC or using the public key
 /// for RSA
 ///
 /// `signature` is the signature part of a jwt (text after the second '.')
+///
 /// `signing_input` is base64(header) + "." + base64(claims)
 pub fn verify(signature: &str, signing_input: &str, key: &[u8], algorithm: Algorithm) -> Result<bool> {
     match algorithm {
@@ -131,9 +138,9 @@ macro_rules! expect_two {
     }}
 }
 
-/// Decode a token into a struct containing Claims and Header
+/// Decode a token into a struct containing 2 fields: `claims` and `header`.
 ///
-/// If the token or its signature is invalid, it will return an error
+/// If the token or its signature is invalid or the claims fail validation, it will return an error.
 pub fn decode<T: Deserialize>(token: &str, key: &[u8], algorithm: Algorithm, validation: Validation) -> Result<TokenData<T>> {
     let (signature, signing_input) = expect_two!(token.rsplitn(2, '.'));
 
diff --git a/src/errors.rs b/src/errors.rs
index c243760..729ab51 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -60,9 +60,9 @@ error_chain! {
     }
 
     foreign_links {
-        Unspecified(ring::error::Unspecified);
-        Base64(base64::Base64Error);
-        Json(serde_json::Error);
-        Utf8(::std::string::FromUtf8Error);
+        Unspecified(ring::error::Unspecified) #[doc = "An error happened while signing/verifying a token with RSA"];
+        Base64(base64::Base64Error) #[doc = "An error happened while decoding some base64 text"];
+        Json(serde_json::Error) #[doc = "An error happened while serializing/deserializing JSON"];
+        Utf8(::std::string::FromUtf8Error) #[doc = "An error happened while trying to convert the result of base64 decoding to a String"];
     }
 }
diff --git a/src/header.rs b/src/header.rs
index 0bd7703..591074d 100644
--- a/src/header.rs
+++ b/src/header.rs
@@ -2,35 +2,61 @@ use crypto::Algorithm;
 
 
 /// A basic JWT header, the alg defaults to HS256 and typ is automatically
-/// set to `JWT`. All the other fields are optional
+/// set to `JWT`. All the other fields are optional.
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 pub struct Header {
+    /// The type of JWS: it can only be "JWT" here
+    ///
+    /// Defined in [RFC7515#4.1.9](https://tools.ietf.org/html/rfc7515#section-4.1.9).
     typ: String,
+    /// The algorithm used
+    ///
+    /// Defined in [RFC7515#4.1.1](https://tools.ietf.org/html/rfc7515#section-4.1.1).
     pub alg: Algorithm,
+    /// Content type
+    ///
+    /// Defined in [RFC7519#5.2](https://tools.ietf.org/html/rfc7519#section-5.2).
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub cty: Option<String>,
+    /// JSON Key URL
+    ///
+    /// Defined in [RFC7515#4.1.2](https://tools.ietf.org/html/rfc7515#section-4.1.2).
     #[serde(skip_serializing_if = "Option::is_none")]
     pub jku: Option<String>,
+    /// Key ID
+    ///
+    /// Defined in [RFC7515#4.1.4](https://tools.ietf.org/html/rfc7515#section-4.1.4).
     #[serde(skip_serializing_if = "Option::is_none")]
     pub kid: Option<String>,
+    /// X.509 URL
+    ///
+    /// Defined in [RFC7515#4.1.5](https://tools.ietf.org/html/rfc7515#section-4.1.5).
     #[serde(skip_serializing_if = "Option::is_none")]
     pub x5u: Option<String>,
+    /// X.509 certificate thumbprint
+    ///
+    /// Defined in [RFC7515#4.1.7](https://tools.ietf.org/html/rfc7515#section-4.1.7).
     #[serde(skip_serializing_if = "Option::is_none")]
     pub x5t: Option<String>,
 }
 
 impl Header {
+    /// Returns a JWT header with the algorithm given
     pub fn new(algorithm: Algorithm) -> Header {
         Header {
             typ: "JWT".to_string(),
             alg: algorithm,
+            cty: None,
             jku: None,
             kid: None,
             x5u: None,
-            x5t: None
+            x5t: None,
         }
     }
 }
 
 impl Default for Header {
+    /// Returns a JWT header using HS256
     fn default() -> Header {
         Header::new(Algorithm::HS256)
     }
diff --git a/src/lib.rs b/src/lib.rs
index add2702..1a2567d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,7 @@
 //! Create and parses JWT (JSON Web Tokens)
 //!
 #![recursion_limit = "300"]
+#![deny(missing_docs)]
 
 #[macro_use]
 extern crate error_chain;
@@ -13,6 +14,7 @@ extern crate ring;
 extern crate untrusted;
 extern crate chrono;
 
+/// All the errors, generated using error-chain
 pub mod errors;
 mod header;
 mod crypto;
diff --git a/src/serialization.rs b/src/serialization.rs
index 41df835..fe7529e 100644
--- a/src/serialization.rs
+++ b/src/serialization.rs
@@ -8,7 +8,7 @@ use errors::{Result};
 use header::Header;
 
 
-/// The return type of a successful call to decode(...)
+/// The return type of a successful call to decode
 #[derive(Debug)]
 pub struct TokenData<T: Deserialize> {
     pub header: Header,
diff --git a/src/validation.rs b/src/validation.rs
index 5a8a67c..4a2cf4e 100644
--- a/src/validation.rs
+++ b/src/validation.rs
@@ -6,20 +6,74 @@ use serde_json::map::Map;
 use errors::{Result, ErrorKind};
 
 
+/// Contains the various validations that are applied after decoding a token.
+///
+/// All time validation happen on UTC timestamps.
+/// ```rust
+/// use jsonwebtoken::Validation;
+///
+/// // Default value
+/// let validation = Validation::default();
+/// // Changing one parameter
+/// let mut validation = Validation {leeway: 1000 * 60, ..Default::default()};
+/// // Setting audience
+/// let mut validation = Validation::default();
+/// validation.set_audience(&"Me"); // string
+/// validation.set_audience(&["Me", "You"]); // array of strings
+/// ```
 #[derive(Debug, Clone, PartialEq)]
 pub struct Validation {
+    /// Add some leeway (in ms) to the `exp`, `iat` and `nbf` validation to
+    /// account for clock skew.
+    ///
+    /// Defaults to `0`.
     pub leeway: i64,
+    /// Whether to actually validate the signature of the token.
+    ///
+    /// WARNING: only set that to false if you know what you are doing.
+    ///
+    /// Defaults to `true`.
     pub validate_signature: bool,
+    /// Whether to validate the `exp` field.
+    ///
+    /// It will return an error if the time in the `exp` field is past.
+    ///
+    /// Defaults to `true`.
     pub validate_exp: bool,
+    /// Whether to validate the `iat` field.
+    ///
+    /// It will return an error if the time in the `iat` field is in the future.
+    ///
+    /// Defaults to `true`.
     pub validate_iat: bool,
+    /// Whether to validate the `nbf` field.
+    ///
+    /// It will return an error if the current timestamp is before the time in the `nbf` field.
+    ///
+    /// Defaults to `true`.
     pub validate_nbf: bool,
-
+    /// If it contains a value, the validation will check that the `aud` field is the same as the
+    /// one provided and will error otherwise.
+    /// Since `aud` can be either a String or a Vec<String> in the JWT spec, you will need to use
+    /// the [set_audience](struct.Validation.html#method.set_audience) method to set it.
+    ///
+    /// Default to `None`.
     pub aud: Option<Value>,
+    /// If it contains a value, the validation will check that the `iss` field is the same as the
+    /// one provided and will error otherwise.
+    ///
+    /// Default to None
     pub iss: Option<String>,
+    /// If it contains a value, the validation will check that the `sub` field is the same as the
+    /// one provided and will error otherwise.
+    ///
+    /// Default to `None`.
     pub sub: Option<String>,
 }
 
 impl Validation {
+    /// Since `aud` can be either a String or an array of String in the JWT spec, this method will take
+    /// care of serializing the value.
     pub fn set_audience<T: Serialize>(&mut self, audience: &T) {
         self.aud = Some(to_value(audience).unwrap());
     }