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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so safety is covered. The description adds real value the annotations cannot: the metric vocabulary returned and the time-window semantics (Moscow time, inclusive dates, default 30 days, days=0 meaning all time). No output schema exists, so disclosing the return shape here is genuinely useful.

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?

Front-loads the purpose, then the return payload, then the period rules — a sensible order. Dense but nearly every clause adds an actionable detail; the long metric enumeration could be trimmed slightly.

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 read-only stats tool with no output schema, the description supplies both the return-payload structure and the full date-window contract, which is what an agent needs to call it correctly. Only sibling routing guidance is missing.

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 0%, so the description carries the burden and does so for the date parameters: since/until are YYYY-MM-DD, inclusive, Moscow time; omitted means last `days` (default 30); days=0 means all time. Only link_id is left implicit, which is acceptable given the name.

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: returns what a single short link produced over a period, and enumerates the metric groups (funnel, daily, paths, referrers, devices). It implicitly distinguishes itself from siblings like question_stats or check_funnel by scoping to one link, but never names those alternatives 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?

Usage is implied rather than stated: the worked example ("сколько оплат дал ролик за сентябрь") shows a valid call, but there is no when-to-use/when-not guidance and no routing against the many sibling read tools.

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