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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so safety is covered. The description adds genuinely new behavioral context: the result set is very large ('The list is long') and should be narrowed with query/limit, which an agent cannot infer from 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?

Three short sentences, front-loaded with what the tool returns before the usage advice. The trailing 'GET /v2/locations' is mildly redundant metadata but does not bloat the definition.

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 simple, annotation-covered, two-parameter lookup with no output schema, the description covers what is returned, why the result is large, and how to narrow it. Only the relationship to the sibling reference-list tools is left implicit.

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 100%, so the schema already documents both parameters, including the example 'vienna' and the match semantics. The description's 'keep only entries that contain it' and 'cap the count' essentially restate the schema, adding little beyond the baseline.

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 precisely what the tool returns (Google's canonical geo locations) and, crucially, its role as the source of valid values for the `location` parameter used by the search tools. That ties it to a concrete consumer and separates it from sibling lookup tools like list_countries or list_languages.

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?

Explains how to use it ('pass query to keep only entries that contain it, and limit to cap the count'), which is real operational guidance. It implies the context (fetch valid location values) but never explicitly contrasts with the other reference-list siblings, so it stops short of full when/when-not routing.

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