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

Annotations already declare readOnly, idempotent, closed-world and non-destructive, so safety is covered. The description adds one meaningful scoping fact beyond the annotations — that only places with well contractors are returned, not all geography — which is a non-obvious filter. It says nothing about ordering, pagination, or whether results are nested country→region→city or a flat list.

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?

One short sentence with no filler and the scope qualifier ('that have well contractors') placed before any other detail. It is efficiently front-loaded, though it leaves the reader wanting the result shape.

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?

With no parameters and no output schema, the description is the only place an agent can learn what comes back, and it only says which entity types appear. Whether the response is a flat array of place objects or a nested country/region/city tree, and how those values are meant to be used in later queries, is left unstated.

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 the schema carries no parameter semantics to clarify and the baseline applies. The description correctly implies the result set is entirely determined server-side, with no filtering options exposed.

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 specific verb (list) and a specific resource (countries, regions and cities with well contractors), so the domain is unambiguous. It does not explicitly contrast itself with sibling enumerations like list_categories or list_sources, but the geographic scope makes the purpose clear.

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 mention that this is the lookup to call before filtering listings by location, and no statement of when it is not appropriate. The agent must infer that this is a reference-data endpoint from the description alone.

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