get_countries_list

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, covering the safety profile. The description adds that the result includes phone codes and that lang_code controls the language of names, but this is content semantics rather than behavioral side effects. No extra context like rate limits or auth is provided.

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?

The description consists of two short sentences: the first states the purpose, and the second explains the argument. Every word earns its place, with no redundant or extraneous 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?

Given the tool's simplicity, the presence of an output schema, and strong annotations, the description provides sufficient context. It states what is returned (all countries with phone codes) and the parameter's effect. No additional details like pagination or authentication are necessary.

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 schema provides only a string type, title, and default for lang_code with no description. The description fills the gap by explaining lang_code values ('en', 'ru', etc.) and its meaning (язык названий), which is essential for correct invocation. It compensates well for the 0% schema coverage, though the full set of codes is left open-ended.

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?

The description opens with 'Список всех стран с phone-кодами' (List of all countries with phone codes), which clearly identifies the tool as a list operation returning country data. This specific verb+resource combination distinguishes it from all sibling tools, which focus on messaging, chats, and account management.

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 parenthetical '(для интерфейса добавления контактов)' specifies the intended use case—contact addition UI—providing clear context for when to invoke this tool. It does not mention exclusions or alternatives, but no alternative exists among the sibling tools.

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