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

Annotations already indicate read-only, idempotent, non-destructive behavior. The description adds transparency about limitations: 'Examples are not validation masks' and 'English fallback and unsupported editorial coverage are explicit.' These clarify edge cases and fallback semantics beyond the annotations.

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?

The description is two sentences, front-loaded with the core purpose, and contains no fluff. Every sentence adds meaning: the first states what is retrieved, the second clarifies important caveats.

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?

Given the tool is simple (two parameters, no nested objects) and has an output schema, the description adequately covers purpose and behavioral caveats. The missing parameter explanations are a minor gap given the self-evident names, but the description does not fully cover all relevant aspects for an agent to use it confidently.

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% and the description provides no explanation of the 'locale' and 'countryCode' parameters. While parameter names are somewhat self-explanatory, the rubric requires the description to compensate for missing schema descriptions; it does not.

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 uses the specific verb 'Get' and identifies the exact resource: 'reviewed display placeholders and trunk-prefix guidance.' This clearly distinguishes it from sibling tools like get_dialing_instructions or get_phone_capabilities by stating its unique output focus.

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?

The description implies usage (when placeholders or trunk-prefix guidance are needed) but does not explicitly state when to prefer this tool over alternatives or provide exclusion criteria. The cautions about validation masks and fallback behavior give context but not directive guidance.

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