diff --git a/include/axolotl/axolotl.hh b/include/axolotl/axolotl.hh
index e333dbc..75c5eb5 100644
--- a/include/axolotl/axolotl.hh
+++ b/include/axolotl/axolotl.hh
@@ -13,94 +13,154 @@ static const size_t AXOLOTL_MESSAGE_TYPE_MESSAGE = 1;
 struct AxolotlAccount;
 struct AxolotlSession;
 
+/** The size of an account object in bytes */
 size_t axolotl_account_size();
 
+/** The size of a session object in bytes */
 size_t axolotl_session_size();
 
+/** Initialise an account object using the supplied memory
+ *  The supplied memory must be at least axolotl_account_size() bytes */
 AxolotlAccount * axolotl_account(
     void * memory
 );
 
+/** Initialise a session object using the supplied memory
+ *  The supplied memory must be at least axolotl_session_size() bytes */
 AxolotlSession * axolotl_session(
     void * memory
 );
 
+/** The value that axolotl will return from a function if there was an error */
 size_t axolotl_error();
 
+/** A null terminated string describing the most recent error to happen to an
+ * account */
 const char * axolotl_account_last_error(
     AxolotlSession * account
 );
 
+/** A null terminated string describing the most recent error to happen to a
+ * session */
 const char * axolotl_session_last_error(
     AxolotlSession * session
 );
 
+/** Returns the number of bytes needed to store an account */
 size_t axolotl_pickle_account_length(
     AxolotlAccount * account
 );
 
+/** Returns the number of bytes needed to store a session */
 size_t axolotl_pickle_session_length(
     AxolotlSession * session
 );
 
+/** Stores an account as a base64 string. Encrypts the account using the
+ * supplied key. Returns the length of the pickled account on success.
+ * Returns axolotl_error() on failure. If the pickle output buffer
+ * is smaller than axolotl_pickle_account_length() then
+ * axolotl_account_last_error() will be "OUTPUT_BUFFER_TOO_SMALL" */
 size_t axolotl_pickle_account(
     AxolotlAccount * account,
     void const * key, size_t key_length,
     void * pickled, size_t pickled_length
 );
 
+/** Stores a session as a base64 string. Encrypts the session using the
+ * supplied key. Returns the length of the pickled session on success.
+ * Returns axolotl_error() on failure. If the pickle output buffer
+ * is smaller than axolotl_pickle_session_length() then
+ * axolotl_session_last_error() will be "OUTPUT_BUFFER_TOO_SMALL" */
 size_t axolotl_pickle_session(
     AxolotlSession * session,
     void const * key, size_t key_length,
     void * pickled, size_t pickled_length
 );
 
+/** Loads an account from a pickled base64 string. Decrypts the account using
+ * the supplied key. Returns axolotl_error() on failure. If the key doesn't
+ * match the one used to encrypt the account then axolotl_account_last_error()
+ * will be "BAD_ACCOUNT_KEY". If the base64 couldn't be decoded then
+ * axolotl_account_last_error() will be "INVALID_BASE64". */
 size_t axolotl_unpickle_account(
     AxolotlAccount * account,
     void const * key, size_t key_length,
     void * pickled, size_t pickled_length
 );
 
+/** Loads a session from a pickled base64 string. Decrypts the session using
+ * the supplied key. Returns axolotl_error() on failure. If the key doesn't
+ * match the one used to encrypt the account then axolotl_session_last_error()
+ * will be "BAD_ACCOUNT_KEY". If the base64 couldn't be decoded then
+ * axolotl_session_last_error() will be "INVALID_BASE64". */
 size_t axolotl_unpickle_session(
     AxolotlSession * session,
     void const * key, size_t key_length,
     void * pickled, size_t pickled_length
 );
 
+/** The number of random bytes needed to create an account.*/
 size_t axolotl_create_account_random_length(
     AxolotlAccount * account
 );
 
+/** Creates a new account. Returns axolotl_error() on failure. If weren't
+ * enough random bytes then axolotl_account_last_error() will be
+ * "NOT_ENOUGH_RANDOM" */
 size_t axolotl_create_account(
     AxolotlAccount * account,
     void const * random, size_t random_length
 );
 
+/** The size of the output buffer needed to hold the identity keys */
 size_t axolotl_account_identity_keys_length(
     AxolotlAccount * account
 );
 
+/** Writes the public parts of the identity keys for the account into the
+ * identity_keys output buffer. The output is formatted as though it was
+ * created with sprintf(output, "[[%10d,\"%43s\"]\n]", key_id, key_base64).
+ * The output can either be parsed as fixed width using the above format or by
+ * a JSON parser. Returns axolotl_error() on failure. If the identity_keys
+ * buffer was too small then axolotl_account_last_error() will be
+ * "OUTPUT_BUFFER_TOO_SMALL". */
 size_t axolotl_account_identity_keys(
     AxolotlAccount * account,
     void * identity_keys, size_t identity_key_length
 );
 
+/** The size of the output buffer needed to hold the one time keys */
 size_t axolotl_account_one_time_keys_length(
     AxolotlAccount * account
 );
 
+/** Writes the public parts of the one time keys for the account into the
+ * one_time_keys output buffer. The first key will be formatted as though it was
+ * created with sprintf(output, "[[%10d,\"%43s\"]\n", key_id, key_base64).
+ * subsequent keys are formatted with ",[%10d,\"%43s\"]\n". The final byte of
+ * output will be "]". The output can either be parsed as fixed width using
+ * the above format or by a JSON parser. Returns axolotl_error() on failure.
+ * If the one_time_keys buffer was too small then axolotl_account_last_error()
+ * will be "OUTPUT_BUFFER_TOO_SMALL". */
 size_t axolotl_account_one_time_keys(
     AxolotlAccount * account,
-    void * identity_keys, size_t identity_key_length
+    void * one_time_keys, size_t one_time_keys_length
 );
 
 /* TODO: Add methods for marking keys as used, generating new keys, and
  * tracking which keys have been uploaded to the central servers */
 
+/** The number of random bytes needed to create an outbound session */
 size_t axolotl_create_outbound_session_random_length(
     AxolotlSession * session
 );
 
+/** Creates a new out-bound session for sending messages to a given identity_key
+ * and one_time_key. Returns axolotl_error() on failure. If the keys couldn't be
+ * decoded as base64 then axolotl_session_last_error() will be "INVALID_BASE64"
+ * If there weren't enough random bytes then axolotl_session_last_error() will
+ * be "NOT_ENOUGH_RANDOM". */
 size_t axolotl_create_outbound_session(
     AxolotlSession * session,
     AxolotlAccount * account,
@@ -110,35 +170,67 @@ size_t axolotl_create_outbound_session(
     void const * random, size_t random_length
 );
 
+/** Create a new in-bound session for sending/receiving messages from an
+ * incoming PRE_KEY message. Returns axolotl_error() on failure. If the base64
+ * couldn't be decoded then axolotl_session_last_error will be "INVALID_BASE64".
+ * If the message was for an unsupported protocol version then
+ * axolotl_session_last_error() will be "BAD_MESSAGE_VERSION". If the message
+ * couldn't be decoded then then axolotl_session_last_error() will be
+ * "BAD_MESSAGE_FORMAT". If the message refers to an unknown one time
+ * key then axolotl_session_last_error() will be "BAD_MESSAGE_KEY_ID". */
 size_t axolotl_create_inbound_session(
     AxolotlSession * session,
     AxolotlAccount * account,
     void * one_time_key_message, size_t message_length
 );
 
+/** Checks if the PRE_KEY message is for this in-bound session. This can happen
+ * if multiple messages are sent to this account before this account sends a
+ * message in reply. Returns axolotl_error() on failure. If the base64
+ * couldn't be decoded then axolotl_session_last_error will be "INVALID_BASE64".
+ * If the message was for an unsupported protocol version then
+ * axolotl_session_last_error() will be "BAD_MESSAGE_VERSION". If the message
+ * couldn't be decoded then then axolotl_session_last_error() will be
+ * "BAD_MESSAGE_FORMAT". */
 size_t axolotl_matches_inbound_session(
     AxolotlSession * session,
     void * one_time_key_message, size_t message_length
 );
 
+/** Removes the one time keys that the session used from the account. Returns
+ * axolotl_error() on failure. If the account doesn't have any matching one time
+ * keys then axolotl_account_last_error() will be "BAD_MESSAGE_KEY_ID". */
 size_t axolotl_remove_one_time_keys(
     AxolotlAccount * account,
     AxolotlSession * session
 );
 
+/** The type of the next message that axolotl_encrypt() will return. Returns
+ * AXOLOTL_MESSAGE_TYPE_PRE_KEY if the message will be a PRE_KEY message.
+ * Returns AXOLOTL_MESSAGE_TYPE_MESSAGE if the message will be a normal message.
+ * Returns axolotl_error on failure. */
 size_t axolotl_encrypt_message_type(
     AxolotlSession * session
 );
 
+/** The number of random bytes needed to encrypt the next message. */
 size_t axolotl_encrypt_random_length(
     AxolotlSession * session
 );
 
+/** The size of the next message in bytes for the given number of plain-text
+ * bytes. */
 size_t axolotl_encrypt_message_length(
     AxolotlSession * session,
     size_t plaintext_length
 );
 
+/** Encrypts a message using the session. Returns the length of the message in
+ * bytes on success. Writes the message as base64 into the message buffer.
+ * Returns axolotl_error() on failure. If the message buffer is too small then
+ * axolotl_session_last_error() will be "OUTPUT_BUFFER_TOO_SMALL". If there
+ * weren't enough random bytes then axolotl_session_last_error() will be
+ * "NOT_ENOUGH_RANDOM". */
 size_t axolotl_encrypt(
     AxolotlSession * session,
     void const * plaintext, size_t plaintext_length,
@@ -146,12 +238,30 @@ size_t axolotl_encrypt(
     void * message, size_t message_length
 );
 
+/** The maximum number of bytes of plain-text a given message could decode to.
+ * The actual size could be different due to padding. Returns axolotl_error()
+ * on failures. If the message base64 couldn't be decoded then
+ * axolotl_session_last_error() will be "INVALID_BASE64". If the message
+ * is for an unsupported version of the protocol then
+ * axolotl_session_last_error() will be "BAD_MESSAGE_VERSION". If the message
+ * couldn't be decoded then axolotl_session_last_error() will be
+ * "BAD_MESSAGE_FORMAT". */
 size_t axolotl_decrypt_max_plaintext_length(
     AxolotlSession * session,
     size_t message_type,
     void * message, size_t message_length
 );
 
+/** Decrypts a message using the session. Returns the length of the plain-text
+ * on success. Returns axolotl_error() on failure. If the plain-text buffer
+ * is smaller than axolotl_decrypt_max_plaintext_length() then
+ * axolotl_session_last_error() will be "OUTPUT_BUFFER_TOO_SMALL". If the
+ * base64 couldn't be decoded then axolotl_session_last_error() will be
+ * "INVALID_BASE64". If the message is for an unsupported version of the
+ * protocol then axolotl_session_last_error() will be "BAD_MESSAGE_VERSION".
+ * If the message couldn't be decoded then axolotl_session_last_error() will be
+ * "BAD_MESSAGE_FORMAT". If the MAC on the message was invalid then
+ * axolotl_session_last_error() will be "BAD_MESSAGE_MAC". */
 size_t axolotl_decrypt(
     AxolotlSession * session,
     size_t message_type,
diff --git a/src/axolotl.cpp b/src/axolotl.cpp
index c195a7c..f03a01c 100644
--- a/src/axolotl.cpp
+++ b/src/axolotl.cpp
@@ -341,7 +341,7 @@ void output_key(
 size_t axolotl_account_identity_keys_length(
     AxolotlAccount * account
 ) {
-    return OUTPUT_KEY_LENGTH * 2 + 1;
+    return OUTPUT_KEY_LENGTH + 1;
 }
 
 
@@ -358,7 +358,6 @@ size_t axolotl_account_identity_keys(
     std::uint8_t * output = from_c(identity_keys);
     output_key(from_c(account)->identity_key, '[', output);
     output += OUTPUT_KEY_LENGTH;
-    output += OUTPUT_KEY_LENGTH;
     output[0] = ']';
     return length;
 }