diff --git a/include/psa/crypto.h b/include/psa/crypto.h
index 9c303cb..ddc86cd 100644
--- a/include/psa/crypto.h
+++ b/include/psa/crypto.h
@@ -3298,7 +3298,8 @@
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  *         \c step is not compatible with the operation's algorithm.
  * \retval #PSA_ERROR_INVALID_ARGUMENT
- *         \c step does not allow key inputs.
+ *         \c step does not allow key inputs of the given type
+ *         or does not allow key inputs at all.
  * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
  * \retval #PSA_ERROR_COMMUNICATION_FAILURE
  * \retval #PSA_ERROR_HARDWARE_FAILURE
@@ -3368,6 +3369,8 @@
  *         \c private_key.
  * \retval #PSA_ERROR_NOT_SUPPORTED
  *         \c alg is not supported or is not a key derivation algorithm.
+ * \retval #PSA_ERROR_INVALID_ARGUMENT
+ *         \c step does not allow an input resulting from a key agreement.
  * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
  * \retval #PSA_ERROR_COMMUNICATION_FAILURE
  * \retval #PSA_ERROR_HARDWARE_FAILURE
diff --git a/include/psa/crypto_values.h b/include/psa/crypto_values.h
index b3e0940..57d0651 100644
--- a/include/psa/crypto_values.h
+++ b/include/psa/crypto_values.h
@@ -1618,31 +1618,39 @@
 
 /** A secret input for key derivation.
  *
- * This must be a key of type #PSA_KEY_TYPE_DERIVE.
+ * This should be a key of type #PSA_KEY_TYPE_DERIVE
+ * (passed to psa_key_derivation_input_key())
+ * or the shared secret resulting from a key agreement
+ * (obtained via psa_key_derivation_key_agreement()).
+ * It can also be a direct input (passed to key_derivation_input_bytes()).
  */
 #define PSA_KEY_DERIVATION_INPUT_SECRET     ((psa_key_derivation_step_t)0x0101)
 
 /** A label for key derivation.
  *
- * This must be a direct input.
+ * This should be a direct input.
+ * It can also be a key of type #PSA_KEY_TYPE_RAW_DATA.
  */
 #define PSA_KEY_DERIVATION_INPUT_LABEL      ((psa_key_derivation_step_t)0x0201)
 
 /** A salt for key derivation.
  *
- * This must be a direct input.
+ * This should be a direct input.
+ * It can also be a key of type #PSA_KEY_TYPE_RAW_DATA.
  */
 #define PSA_KEY_DERIVATION_INPUT_SALT       ((psa_key_derivation_step_t)0x0202)
 
 /** An information string for key derivation.
  *
- * This must be a direct input.
+ * This should be a direct input.
+ * It can also be a key of type #PSA_KEY_TYPE_RAW_DATA.
  */
 #define PSA_KEY_DERIVATION_INPUT_INFO       ((psa_key_derivation_step_t)0x0203)
 
 /** A seed for key derivation.
  *
- * This must be a direct input.
+ * This should be a direct input.
+ * It can also be a key of type #PSA_KEY_TYPE_RAW_DATA.
  */
 #define PSA_KEY_DERIVATION_INPUT_SEED       ((psa_key_derivation_step_t)0x0204)