webhook_limit_reached
Status 409. This account already has as many webhook endpoints as it may.
What it means
The account already has 5 enabled webhook endpoints, the most it may have. max_endpoints says so. A disabled endpoint does not count.
What to do
Delete one you no longer need with DELETE /webhooks/{endpoint_id}, then create the new one.
Safe to send again?
Not as it is. Change what the answer points to, then send the request.
What else the answer carries
max_endpoints: How many enabled endpoints an account may have.
Where you can meet it
POST /webhooks: Send points movements to an https endpoint
Every code, and the shape of an error answer: Errors.