Accepted answer
Check the SURMOUNT-5 inclusion criteria against yourself in that order: entry BMI band, diabetes status, prior weight-loss attempts, and what the run-in excluded. Registration programmes recruit a population selected to show an effect if one exists, which is the right design and a poor basis for generalising. The run-in is the part that is easiest to miss: a programme that drops people during a placebo lead-in has already removed those least likely to tolerate or comply, and the published arms describe the survivors. External validity is not a property of the trial; it is a property of the distance between its population and yours, and that distance is yours to measure.
The part that matters: a trial establishes what happened to a defined group under a defined protocol. Extending it beyond that group is inference, and inference is allowed as long as it is labelled.
Duration decides what can be seen. A 68-week trial can measure weight and glycaemia; it cannot measure anything whose event rate is one per cent per year without enrolling tens of thousands.
The underlying point is that intention-to-treat and per-protocol analyses answer different questions. ITT asks what happens if you offer the treatment; per-protocol asks what happens if it is taken as directed. The gap between the two is a measure of how tolerable the protocol was.
Registry entries at ClinicalTrials.gov carry the pre-specified primary endpoint with a timestamp, which is the cheapest available check on whether an endpoint was changed after the data were seen.
The short version: check the endpoint, check the comparator, check who was excluded, then look at the number.