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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is fully covered. The description adds the demo-mode restriction, which is a genuine behavioral trait beyond annotations. But it does not clarify what 'reliability' means as a metric, what happens for unsupported routes, or the historical date range covered.

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 two sentences and front-loads the core purpose before the constraint. The route list is somewhat long but carries necessary demo-mode information. Nothing is wasted, though the enumeration could arguably be condensed.

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 query tool with only three well-documented parameters and safety annotations, the description covers the basics. However, there is no output schema, so the agent must infer what a reliability result looks like; the meaning of the reliability metric and the behavior on unsupported routes are also left unspecified. Adequate but with clear gaps.

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 the baseline is 3. The description adds value by listing concrete origin-destination pairs (ATL-LGA, ORD-EWR, etc.) that are actually loadable in demo mode, which tells the agent which parameter combinations will succeed beyond the schema's generic format examples. This justifies one point above baseline.

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 opens with a clear verb-plus-resource statement: 'Return historical route reliability.' The word 'route' helps separate it from the sibling flight_airline_reliability. However, it does not explicitly distinguish itself from overlapping siblings like flight_cancellation_risk, flight_route_summary, or flight_route_best_times, so it stops short of full differentiation.

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 description provides operational context by noting that 'Demo mode allows selected loaded routes' and enumerates the six supported route pairs. This implies when the tool can actually return data in demo environments, but it never states when to prefer this tool over the related flight tools or what conditions would select an alternative.

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