In Ontario the only legal document that is required for you to have a service dog accompanying you is a Dr’s note. Generally this is on a regular prescription header paper and is usually updated once a year. Your Dr may charge a fee to update your prescription.
You are not required to state what your disability is unless you need your Dr’s note for flying.
For example:
To whom it may concern,
(Your name)(Your Details i.e DOB , Health #)
The above mentioned has a medical condition for which a service dog is required.
Should you need to use air travel, your carrier might require you to state your disability according to DSM-IV (Diagnostic and Statistical Manual of Mental Disorders).