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

Beyond the readOnly/openWorld/idempotent annotations, the description discloses non-obvious behavior: results are derived from historical observations, reliability is tiered (5+ obs is high-confidence but not a guarantee, 0-1 obs is just the fleet prior), and coverage varies materially by flight-number range. This gives the agent the right expectations and cautions, and it does not contradict the annotations.

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, each carrying distinct information: use condition, result definition, reliability caveat, and fleet-split alternative. It is front-loaded and free of filler.

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?

The tool is simple (2 params, 1 required), annotations already cover the safety profile, and the schema documents the optional date side effect. The description contributes reliability and coverage context, so an agent has enough to select and invoke the tool correctly despite lacking an output schema.

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 the baseline is 3; the description adds interpretation value by explaining coverage differences across flight-number ranges and directing the agent to get_fleet_stats for the current split. Parameter syntax and date behavior are already thoroughly handled in the schema, so no higher score is warranted.

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 concrete trigger ('will my flight have Starlink?') and defines the operation as returning a probability that a United flight number gets a Starlink plane from historical observations. It also scopes use to future/no-date cases, which distinguishes it from confirmed-assignment lookups and from fleet-level tools.

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?

It explicitly says when to use the tool (date too far out for a confirmed assignment, or no date) and provides a when-not/alternative by telling the agent to call get_fleet_stats for the current UA1-2999 vs UA3000-6999 split rather than assuming a rate. This is concrete routing guidance with a named sibling.

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