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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds 'historical' and 'not live tracking,' which adds context about the temporal nature of the data. But it doesn't disclose how missing data is handled, what 'best time bucket' means, or any rate limits. With annotations carrying the safety profile, the description provides minimal but useful additional context.

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 description is exactly two sentences with zero redundancy. The first sentence front-loads the primary purpose and content, and the second sentence is a concise clarification. Every word earns its place.

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 simple two-param tool with safe annotations, the description lists the key output components, which is helpful. However, it omits any mention of the output format (since no output schema exists), and given the large number of flight siblings, it doesn't explicitly explain when this combined view is more appropriate than the focused tools. It is adequate but not comprehensive.

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 both parameters (origin, dest) are already described as airport codes with examples. The description doesn't add extra meaning beyond 'route,' such as format enforcement or coordinate vs. code. Since the schema fully documents the parameters, the description does not need to compensate, earning the baseline 3.

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 uses a specific verb ('Return') and resource ('combined historical route summary'), and lists the included data points (reliability, cancellation risk, carriers, months, best time bucket). It distinguishes from live tracking, which helps set expectations. However, it doesn't explicitly differentiate from sibling tools like flight_reliability or flight_cancellation_risk, though the word 'combined' implies aggregation.

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 only usage hint is 'This is not live tracking,' which is a negative clarification but offers no guidance on when to choose this tool over the many flight-specific siblings (e.g., flight_airline_reliability, flight_route_best_times). No explicit conditions or alternatives are mentioned, leaving the agent to infer that the combined summary is preferable for a holistic view.

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