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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true), so the bar is lower. The description adds real value beyond them by disclosing the data source ('Данные из кэша LastBilet'), implying cached, possibly stale results, and by noting flexible-date (±) behaviour in day mode.

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?

A single dense sentence that front-loads the resource and then splits into the two modes; nothing is wasted. It is compact rather than padded, though the mode split could be slightly more scannable.

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, cache-backed lookup with no output schema and no nested objects, the description covers both output granularities and the data source. The only meaningful omission is the undocumented direct_only flag, which no other structured field explains.

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 75%, with origin/destination and month documented in the schema. The description reinforces the meaning of the month switch and adds flexible-date semantics for day mode, but the 25% gap (direct_only) is undocumented in both schema and description. Baseline 3 for good schema coverage plus marginal added meaning.

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 resource and output shape: a minimum-price calendar by route, with two distinct modes (day-level with month, month-level without). It does not differentiate itself from the sibling cheapest_prices, so an agent cannot tell from this text alone which of the two price tools to pick.

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 two operating modes are spelled out (pass month for per-day prices; omit it for a year of monthly prices), which is useful conditional guidance. However there is no when-to-use vs when-not-to-use framing and no pointer to alternatives such as cheapest_prices or search_flights.

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