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

With no annotations, the description carries the full load and does well: it names the data source, the collection cadence ('várias vezes ao dia'), the coverage (round trip 5–15 days plus one-way), the computed aggregates, and that page_url should be cited. It omits any statement about read-only safety, rate limits, or response shape, keeping it short of 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?

The tool's core identity is front-loaded, but the text mixes Portuguese with a trailing English fragment ('Daily price history of a whole route from Brazil') and spends a sentence on example phrasings already implied by the metrics list. Some redundancy for the length.

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?

Returned content is described thoroughly enough that an agent can judge relevance without an output schema, and the Brazil-only scope is flagged. Missing is any routing guidance versus the closely related trip_price_history and price_calendar siblings, which is the main ambiguity for selection.

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 100%, so origin/destination and dias are already documented, giving a 3 baseline. The description repeats the Portuguese city-name support already in the schema, and its reference to 'últimos 30 dias' alongside a separate dias parameter (1–365, default 90) risks confusing which window controls the statistics.

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 scope: historical daily minimum prices for a whole route, sourced from passagens.dev, with the metrics that come back (daily min, 30-day min/max/avg, today vs average). The phrase 'rota inteira' implicitly distinguishes it from trip_price_history and price_calendar, but no sibling is named outright.

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 conveyed only through example questions ('está barato agora?', 'é boa hora para comprar?', 'quando esteve mais barato?'), which implies the right context without stating when to prefer it over trip_price_history, price_calendar, or cheapest_route. No exclusions or prerequisites are given.

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