diff --git a/pr2eus/robot-interface.l b/pr2eus/robot-interface.l
index 2c6501312..071c5a6a9 100644
--- a/pr2eus/robot-interface.l
+++ b/pr2eus/robot-interface.l
@@ -823,28 +823,29 @@
   ;;
   (:go-pos
    (x y &optional (d 0)) ;; [m] [m] [degree]
-   "move robot toward x, y, degree and wait to reach that goal. return t if reached and nil if fail
+   "move robot toward x, y, degree and wait to reach that goal. return t if reached or nil if fail
     the robot moves relative to current position.
     using [m] and [degree] is historical reason from original hrpsys code"
    (warn "subclass's responsibility for (send ~s :go-pos)~%" self))
   (:go-pos-no-wait
    (x y &optional (d 0)) ;; [m] [m] [degree]
-   "no-wait version of :go-pos"
+   "no-wait version of :go-pos. this function is always assumed to return t"
    (warn "subclass's responsibility for (send ~s :go-pos-no-wait)~%" self))
   (:go-wait
    ()
-   "wait until :go-pos-no-wait reached to the goal, return t if reached and nil if fail"
+   "wait until :go-pos-no-wait reached to the goal, return t if reached or nil if fail"
    (warn "subclass's responsibility for (send ~s :go-wait)~%" self))
   (:go-velocity
    (x y d ;; [m/sec] [m/sec] [rad/sec]
     &optional (msec 1000) ;; msec is total animation time [msec]
     &key (stop t) (wait))
-   "move robot at given speed for given msec
-    if stop is t, robot stops after msec, use wait t for blocking call"
+   "move robot at given speed for given msec.
+    if stop is t, robot stops after msec, use wait t for blocking call
+    return nil if aborted while waiting by enabling :wait, otherwise return t"
    (warn "subclass's responsibility for (send ~s :go-velocity)~%" self))
   (:go-stop
    ()
-   "stop go-velocity"
+   "stop go-velocity. return t if robot successfly stops, otherwise return nil"
    (warn "subclass's responsibility for (send ~s :stop)~%" self))
   ) ;; robot-interface
 ;; ros visualization methods