diff --git a/library/psa_crypto_core.h b/library/psa_crypto_core.h
index 91ef0bf..21e7559 100644
--- a/library/psa_crypto_core.h
+++ b/library/psa_crypto_core.h
@@ -88,7 +88,15 @@
     /* The index of the slice containing this slot.
      * This field must be filled if the slot contains a key
      * (including keys being created or destroyed), and can be either
-     * filled or 0 when the slot is free. */
+     * filled or 0 when the slot is free.
+     *
+     * In most cases, the slice index can be deduced from the key identifer.
+     * We keep it in a separate field for robustness (it reduces the chance
+     * that a coding mistake in the key store will result in accessing the
+     * wrong slice), and also so that it's available even on code paths
+     * during creation or destruction where the key identifier might not be
+     * filled in.
+     * */
     uint8_t slice_index;
 #endif /* MBEDTLS_PSA_KEY_STORE_DYNAMIC */
 
diff --git a/library/psa_crypto_slot_management.h b/library/psa_crypto_slot_management.h
index 26b7396..af1208e 100644
--- a/library/psa_crypto_slot_management.h
+++ b/library/psa_crypto_slot_management.h
@@ -137,13 +137,15 @@
  * If multi-threading is enabled, the caller must hold the
  * global key slot mutex.
  *
- * \param[out] volatile_key_id   If null, reserve a cache slot for
- *                               a persistent or built-in key.
- *                               If non-null, allocate a slot for
- *                               a volatile key.
- *                               If non-null, on success, the volatile key
- *                               identifier corresponding with the
- *                               returned slot.
+ * \param[out] volatile_key_id   - If null, reserve a cache slot for
+ *                                 a persistent or built-in key.
+ *                               - If non-null, allocate a slot for
+ *                                 a volatile key. On success,
+ *                                 \p *volatile_key_id is the
+ *                                 identifier corresponding to the
+ *                                 returned slot. It is the caller's
+ *                                 responsibility to set this key identifier
+ *                                 in the attributes.
  * \param[out] p_slot            On success, a pointer to the slot.
  *
  * \retval #PSA_SUCCESS \emptydescription