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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description wisely spends its budget on semantics the annotations cannot express: the exact calendar-day/timezone definition of 'today', the verification criterion (positive saving vs usual price), and the empty-list behavior. It even discloses an extra return field ('plus count').

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?

Four sentences with no waste: the filtering rule comes first, then the usage trigger, then the return shape, then the fallback. Every sentence carries distinct information and the routing guidance is front-loaded.

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?

Despite having no output schema, the description explains the return shape by reference to a sibling ('same fields as list_flight_deals, plus count') and covers the degenerate empty case. For a zero-required-parameter read tool, nothing an agent needs to call it correctly 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 100%, with limit, nights and origin each fully documented including ranges, defaults and the IATA pattern, so the schema does the heavy lifting. The description adds no syntax or meaning beyond the schema for these three parameters, which is the baseline 3 case.

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 states a specific verb and resource ('Return only the strongest current deals') and pins the exact filter: fares whose Google savings insight was checked today (America/Los_Angeles) with a positive saving versus usual price. It also distinguishes itself from the sibling list_flight_deals by framing that tool as 'recent observations' rather than freshly verified deals.

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?

Explicit when-to-use ('when the user asks for today's deals or wants prices that are freshly verified') plus a named alternative and the condition that selects it ('offer list_flight_deals for recent observations'). It also instructs on the empty-result case, telling the agent to say so rather than present older fares.

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