diff --git a/include/osmocom/gsm/mncc.h b/include/osmocom/gsm/mncc.h
index e5e9607..db70235 100644
--- a/include/osmocom/gsm/mncc.h
+++ b/include/osmocom/gsm/mncc.h
@@ -10,10 +10,10 @@
 
 /* Expanded fields from GSM TS 04.08, Table 10.5.102 */
 struct gsm_mncc_bearer_cap {
-	int		transfer;	/* Information Transfer Capability */
-	int 		mode;		/* Transfer Mode */
-	int		coding;		/* Coding Standard */
-	int		radio;		/* Radio Channel Requirement */
+	int		transfer;	/* Information Transfer Capability, see enum gsm48_bcap_itcap. */
+	int 		mode;		/* Transfer Mode, see enum gsm48_bcap_tmod. */
+	int		coding;		/* Coding Standard, see enum gsm48_bcap_coding.*/
+	int		radio;		/* Radio Channel Requirement, see enum gsm48_bcap_rrq. */
 	int		speech_ctm;	/* CTM text telephony indication */
 	int		speech_ver[8];	/* Speech version indication, see enum gsm48_bcap_speech_ver; -1 marks end */
 	struct {
diff --git a/include/osmocom/gsm/protocol/gsm_08_08.h b/include/osmocom/gsm/protocol/gsm_08_08.h
index 9806e08..a540609 100644
--- a/include/osmocom/gsm/protocol/gsm_08_08.h
+++ b/include/osmocom/gsm/protocol/gsm_08_08.h
@@ -512,13 +512,15 @@
 	GSM0808_PAGINF_FOR_USSD		= 0x02,
 };
 
-/* 3GPP TS 48.008 3.2.2.104 Speech Codec */
+/*! 3GPP TS 48.008 3.2.2.104 Speech Codec */
 struct gsm0808_speech_codec {
 	bool fi;
 	bool pi;
 	bool pt;
 	bool tf;
+	/*! See enum gsm0808_speech_codec_type. */
 	uint8_t type;
+	/*! For examples, see enum gsm0808_speech_codec_defaults. */
 	uint16_t cfg;
 };