Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true so the safety profile is covered, and the description adds value with 'and why not', hinting that a denial reason is returned even though no output schema exists. It doesn't disclose what eligibility depends on (subscription tier, org permissions, minutes remaining) or what the response shape looks like.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single front-loaded sentence with no filler, answering the two things an agent needs at a glance (eligibility and reason). It is terse to the point of being a fragment, but nothing is wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Low-complexity read with no params and no output schema, so the description carries the return-value burden. Saying it reports eligibility plus a reason is a start, but it doesn't explain what conditions are evaluated or how a 'can host' result should be interpreted, leaving gaps for an agent deciding whether to proceed with a video call.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so there is nothing for the description to document; baseline 4 applies. The schema is empty and imposes no ambiguity.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States the specific question it answers (can the coach host video calls) and that it may include a reason. It's a clear eligibility-check purpose, but it never differentiates itself from related siblings like get_video_minutes or get_active_trainer_subscription, which also gate video-call capability.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is only implied: an agent can infer this is a pre-flight check before start_instant_video_call or join_session_video_call, but the description never names those alternatives or says when this check is required versus optional.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.