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

Annotations already declare readOnlyHint, idempotentHint and closed-world behavior, so the safety profile is covered. The description adds genuinely non-obvious matching behavior ('prefix match', i.e. not substring or fuzzy) plus the shape of results, which an agent cannot infer from annotations alone.

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 front-loaded sentence covering purpose, match mode, outputs, and downstream use, with a compact bilingual gloss appended. No filler and nothing buried.

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 two-parameter read-only search with no output schema, the description supplies the essentials: what it matches on and what comes back. Minor gaps remain on result ordering and whether multiple city matches are possible, but nothing blocks a correct call.

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 coverage is 100%, so the limit range and query length are already documented. The description still earns credit by specifying that matching is prefix-based, extra semantics about the query parameter that the schema's 'City name, 1-60 chars' does not convey.

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 and resource ('Search cities by name') and enumerates the fields returned (coordinates, country, hotel count, main airport). It also positions the tool against siblings by noting the returned lat/lng feeds the nearby tools, so an agent can distinguish lookup from gil_hotels_nearby/gil_places_nearby without inspecting schemas.

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 sentence 'Returns lat/lng usable as input to the nearby tools' gives clear chaining context: use this first to resolve a city, then call the nearby tools. It stops short of explicit exclusions (e.g., what to do for ambiguous or partial names, or when to prefer country-level data), so no full when/when-not guidance.

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