diff --git a/os/net/app-layer/coap/coap-callback-api.h b/os/net/app-layer/coap/coap-callback-api.h
index 7f144af96..69ceea4f5 100644
--- a/os/net/app-layer/coap/coap-callback-api.h
+++ b/os/net/app-layer/coap/coap-callback-api.h
@@ -65,6 +65,14 @@ struct coap_request_state {
   void (*callback)(coap_request_state_t *state);
 };
 
+/**
+ * \brief Send a CoAP request to a remote endpoint
+ * \param state The state to handle the CoAP request
+ * \param endpoint The destination endpoint
+ * \param request The request to be sent
+ * \param callback callback to execute when the response arrives or the timeout expires
+ * \return 1 if there is a transaction available to send, 0 otherwise
+ */
 int coap_send_request(coap_request_state_t *state, coap_endpoint_t *endpoint,
                        coap_message_t *request,
                        void (*callback)(coap_request_state_t *state));