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

Annotations already cover safety (readOnly, non-destructive, openWorld), but the description adds substantive context: the returned component is authoritative and must not be re-rendered, and null values mean 'no data for that month'. It also discloses the data's provenance ('cheapest one-way ticket found in recent user searches'), which tells the agent the values are search-derived rather than live inventory.

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-loaded with the purpose, then the rendering constraint, then the data semantics. Every sentence is functional, though the closing sentence on monthly contents overlaps with what an output schema already conveys.

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 correctly omits structural return details and instead covers the things the schema cannot express: widget authority, no-duplicate-rendering instruction, and null semantics. Coverage of the tool's behavior is sufficient for correct invocation, though it never clarifies how it relates to the neighboring price tools.

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 all four parameters (locale, originCode, currencyCode, destinationCode) are already fully documented, including the resolve_city_iata_code prerequisite and enum lists. The description adds no parameter-level detail beyond what the schema provides, so the baseline 3 applies.

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 monthly prices and an interactive Flaut.Travel price chart for a city-to-city route'), which is clear and concrete. It does not, however, explicitly distinguish itself from siblings like search_route_prices or render_route_prices, so an agent must infer the boundary.

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?

Provides strong post-invocation guidance ('do not create another chart or table', 'provide only a brief textual takeaway'), which shapes how the result is used. It gives no guidance on when to choose this tool over the sibling price tools, so usage selection remains implied rather than stated.

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