diff --git a/src/gsm/auth_core.c b/src/gsm/auth_core.c
index b78cdd5..f1ec2ed 100644
--- a/src/gsm/auth_core.c
+++ b/src/gsm/auth_core.c
@@ -43,6 +43,7 @@
 
 /*! \brief Register an authentication algorithm implementation with the core
  *  \param[in] impl Structure describing implementation and it's callbacks
+ *  \returns 0 on success, or a negative error code on failure
  *
  * This function is called by an authentication implementation plugin to
  * register itself with the authentication core.
@@ -64,6 +65,7 @@
 
 /*! \brief Load all available authentication plugins from the given path
  *  \param[in] path Path name of the directory containing the plugins
+ *  \returns number of plugins loaded in case of success, negative in case of error
  *
  * This function will load all plugins contained in the specified path.
  */
@@ -75,6 +77,7 @@
 
 /*! \brief Determine if a given authentication algorithm is supported
  *  \param[in] algo Algorithm which should be checked
+ *  \returns 1 if algo is supported, 0 if not, negative error on failure
  *
  * This function is used by an application to determine at runtime if a
  * given authentication algorithm is supported or not.
@@ -111,10 +114,12 @@
 
 /*! \brief Generate 3G CK + IK from 2G authentication vector
  *  \param vec Authentication Vector to be modified
+ *  \returns 1 if the vector was changed, 0 otherwise
  *
  * This function performs the C5 and C4 functions to derive the UMTS key
  * material from the GSM key material in the supplied vector, _if_ the input
- * vector doesn't yet have UMTS authentication capability */
+ * vector doesn't yet have UMTS authentication capability.
+ */
 int osmo_auth_3g_from_2g(struct osmo_auth_vector *vec)
 {
 	if ((vec->auth_types & OSMO_AUTH_TYPE_GSM) &&
@@ -124,7 +129,7 @@
 		/* We cannot actually set OSMO_AUTH_TYPE_UMTS as we have no
 		 * AUTN and no RES, and thus can only perform GSM
 		 * authentication with this tuple.
-		 * */
+		 */
 		return 1;
 	}
 
@@ -135,6 +140,7 @@
  *  \param[out] vec Generated authentication vector
  *  \param[in] aud Subscriber-specific key material
  *  \param[in] _rand Random challenge to be used
+ *  \returns 0 on success, negative error on failure
  *
  * This function performs the core cryptographic function of the AUC,
  * computing authentication triples/quintuples based on the permanent
@@ -167,6 +173,7 @@
  *  \param[in] rand_auts RAND value sent by the SIM/MS
  *  \param[in] auts AUTS value sent by the SIM/MS
  *  \param[in] _rand Random challenge to be used to generate vector
+ *  \returns 0 on success, negative error on failure
  *
  * This function performs a special variant of the  core cryptographic
  * function of the AUC: computing authentication triples/quintuples