If you don't know that your service is down, then you don't know where and what to look for. for monitoring, you need to be looking for a specific parameter or string. if that changes, its very difficult to generate an automated alert.
Fair enough... if you're monitoring "response_time", and a developer changes that field to "time_taken_to_send_the_bits" you'll probably have a tough time monitoring the service. However, if the dev communicates that the value has changed, with the right tool it isn't hard to have something that covers both fields.
100% but in the real world its a bit hard to coordinate.
Ideally you'd have a schema that you agree company wide. Before an app is deployed it has to pass the schema test. At least that would cover most of the basic checks.
but, For most small places, logs are perfectly fine for monitoring, as you imply
If you don't know that your service is down, then you don't know where and what to look for. for monitoring, you need to be looking for a specific parameter or string. if that changes, its very difficult to generate an automated alert.