[request]: emit warning if required arguments are unset

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**Tell us about your request**
If required arguments are unset, customers frequently get bad errors. We should add two mitigations:
- emit tracing log
- add error context when required inputs are unset

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
What outcome are you trying to achieve, ultimately, and why is it hard/impossible to do right now? What is the impact of not having this problem solved? The more details you can provide, the better we'll be able to understand and solve the problem.

**Are you currently working around this issue?**
How are you currently solving this problem?

**Additional context**
Anything else we should know?

**Attachments**
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No files, tests, or entry points are named. Start by locating where required arguments are validated and where tracing logs and request errors are produced; clarify the expected warning and error context, then add focused coverage showing the behavior when required inputs are unset.

Written by the indexing model from the issue text.