Справочники

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds behavior the annotations do not: one dictionary (GeoRegions) is very large, which warns the agent about payload size and the need to avoid it. It says nothing about client_login resolution behavior or response shape, keeping it below a 5.

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 tight sentences with zero filler; the capability statement comes first and the cautionary sibling reference second. Every clause carries usable information.

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 lookup with full schema coverage and annotations, the description supplies what an agent needs to choose and call it correctly. The only residual gap is that return structure is unaddressed and there is no output schema, though the enumerated dictionary kinds largely imply it.

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 both names and client_login are documented in the schema itself, setting the baseline at 3. The description's enumeration of dictionary kinds loosely mirrors the enum values but adds no syntax, limits, or semantics beyond what the schema states.

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 concrete verb and resource ('Возвращает справочники Яндекс Директа') and enumerates representative contents (валюты, часовые пояса, константы, категории объявлений), so the agent knows exactly what kind of data comes back. It also contrasts itself with a sibling, making it distinguishable without opening the schema.

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?

Gives explicit routing for one important case: GeoRegions can be huge, so use get_regions for region lookup instead. That is real when-not guidance. It stops short of stating the general when-to-use framing (e.g. fetch currency/timezone codes before creating campaigns), so it is not fully exhaustive.

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