list_cities

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds the shape of the returned records and the validity constraint on the resulting values, which is useful, but it says nothing about caching, result size, or staleness of the city 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?

Two short sentences, front-loaded with what the tool returns and followed by the actionable constraint on using those values. Every clause earns its place with no 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?

With an output schema present, the description need not enumerate return values, and it correctly covers purpose plus the downstream usage rule. It is nearly complete for a simple zero-parameter lookup; only exhaustiveness/pagination behavior of the list 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 baseline is 4. The description still contributes by explaining how a value drawn from this list should be used as the `city` argument in other calls, adding cross-tool meaning rather than repeating schema content.

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 the resource (the set of cities offered in goldapple.ru's city picker) and the fields returned (name, FIAS city id, region id), so an agent knows exactly what this lookup yields. It does not need heavy sibling differentiation since no sibling deals with cities, but the verb is implied rather than explicit.

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?

'Any of them can be passed as `city`; others are not supported' gives real usage context – the output feeds the `city` parameter elsewhere and constrains valid values. However, it never states when to call this tool (e.g., before a filtered search) versus simply proceeding, so usage is implied rather than prescribed.

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