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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, non-open-world). The description adds real value beyond them by disclosing that availability is volatile and platform access is not guaranteed, which tells the agent to re-query rather than cache. It stops short of saying whether the credit price can change per scan or how it is surfaced.

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?

Two tight sentences with the actionable content (what is checked) front-loaded and the caution second. No filler; slightly more compact than necessary but well structured.

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?

For a read-only capability query with an output schema present, the description need not explain return values, and it correctly focuses on what is checked and when to call it. The only substantive gap is the unaddressed brandId scoping and the ambiguity versus the other *capabilities siblings.

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?

Schema description coverage is 0% for the single required brandId parameter, and the description never mentions it. The rubric requires the description to compensate when coverage is below 50%, and it does not; the agent must infer that the capability check is brand-scoped from the schema name alone.

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?

The description names the specific resource being checked and enumerates the concrete payload: source availability, public ad library allowances, and the current scan credit price. That is enough for an agent to know this is a capability/pricing lookup rather than a listing or mutation. It does not, however, distinguish itself from the three sibling capability tools (get_automation_capabilities, get_report_capabilities, get_workspace_capabilities).

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?

"before researching" gives a clear timing cue, which is genuine usage guidance. But there is no explicit when-not and no differentiation from the sibling capability-lookup tools, so an agent facing four *capabilities tools must infer which one fits.

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