diff --git a/include/mbedtls/ctr_drbg.h b/include/mbedtls/ctr_drbg.h
index 6626024..5955079 100644
--- a/include/mbedtls/ctr_drbg.h
+++ b/include/mbedtls/ctr_drbg.h
@@ -179,6 +179,16 @@
  * \brief               This function seeds and sets up the CTR_DRBG
  *                      entropy source for future reseeds.
  *
+ * A typical choice for the \p f_entropy and \p p_entropy parameters is
+ * to use the entropy module:
+ * - \p f_entropy is mbedtls_entropy_func();
+ * - \p p_entropy is an instance of ::mbedtls_entropy_context initialized
+ *   with mbedtls_entropy_init() (which registers the platform's default
+ *   entropy sources).
+ *
+ * \p f_entropy is always called with a buffer size equal to the entropy
+ * length described in the documentation of mbedtls_ctr_drbg_set_entropy_len().
+ *
  * You can provide a personalization string in addition to the
  * entropy source, to make this instantiation as unique as possible.
  *