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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. Beyond that the description adds only the vague "in plain terms," which hints at human-readable output but does not say what is returned, whether results are per-country, or how missing/unknown countries are handled.

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 short sentence with no filler; the purpose and scope are front-loaded and 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?

This is a simple read-only lookup with no output schema and only two optional params, so the description needn't explain return values. Still, with 0% schema coverage it leaves the accepted input vocabulary (ISO codes? names?) and the meaning of "plain terms" unspecified, which is the minimum an agent would need to call 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%, so the description must carry the burden; it does partially by naming both dimensions ("country" and "number-type"), which maps to the countries and number_types arrays. It gives no format, expected value vocabulary, or behavior for empty/omitted arrays, so compensation is incomplete.

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 a concrete verb ("Return") and a specific resource ("country and number-type onboarding requirements"), so an agent knows this is a read/lookup tool. It does not, however, distinguish itself from adjacent siblings such as get_number_rules, get_number_catalog, or get_coverage, which an agent could easily confuse it with.

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?

There is no when-to-use guidance, no prerequisites, and no mention of alternatives. With several similarly named number-related siblings (get_number_rules, get_number_catalog, get_coverage, request_number), the absence of routing guidance is a real gap.

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