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

Annotations already declare read-only, idempotent, closed-world semantics, so the safety profile is covered. The description adds genuinely new behavior: candidates should be surfaced to the user rather than auto-selected, and there is no nearby-city expansion — a real scope constraint an agent would otherwise assume wrong.

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, each earning its place: what it returns, when to use it, and how to handle the result. The usage cue and the anti-pattern warning are front-loaded with zero filler.

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?

Only two simple parameters and an output schema exists, so return-shape documentation is unnecessary. Usage, scope limits, and the handling policy are all covered; the only omission is guidance on `limit` and on the minimum query length/behavior for very short prefixes.

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 0%, so the description must carry parameter meaning. It does explain that `q` accepts a name prefix or a postal code, which is meaningful added semantics. However, `limit` is never mentioned in the description and its purpose must be inferred from the schema alone.

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 ('Find catalog city slugs') plus the two accepted input modes (name prefix or postal code). It implicitly separates itself from search/catalog siblings by framing the result as slugs for resolution rather than search results, though it never names a sibling explicitly.

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?

'Use before searching when a locality is ambiguous' gives a clear triggering condition and ordering relative to downstream search tools. It stops short of stating when the tool should be skipped (e.g., when the user already supplied a known slug), but the intended workflow is unambiguous.

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