1. A computer-vision based method for validating an activity workflow of a human performer, the method comprising: determining an expected sequence of actions associated with a target activity; receiving a video stream from an image capture device monitoring an activity performed by an associated human performer; determining an external cue in the video stream; associating a frame capturing the external cue as a first frame in a key frame sequence; determining an action being performed by the associated human performer in the key frame sequence; in response to determining the action in the key frame sequence matching an expected action in the target activity, verifying the action as being performed in the monitored activity; and, in response to not determining the action in the key frame sequence, generating an alert indicating an error in the monitored activity.