World Professional Association for Transgender Health is an organization of psychologists, surgeons and many other health care professionals who, over the years have come up with a Standard of Care for transgender patients. Their standard of Care is not static, but changes with new knowledge gained by experience and medical studies.
60 years ago there was no standard of care and the surgeons who did transgender surgery were viewed with some suspicion by the rest of the medical community. To legitimize their efforts, the Harry Benjamin International Gender Dysphoria Association was started and later became the WPATH. This is a world wide association and their work is above reproach.
If your therapist is using WPATH guidelines, your transition will be safe and effective. Most of the trans people here have transitioned under WPATH guideline.