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

Annotations already declare the read-only, idempotent, closed-world safety profile, so the bar is lower. The description adds meaningful provenance beyond them by stating the comparison uses the airport's own posted rates, which tells the agent how much to trust the numbers. It does not say whether taxes/fees are included or how fresh the rates are.

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?

Two sentences, zero filler. The core comparison is front-loaded and the example phrasings come last as reinforcement.

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 two-parameter, read-only comparison tool with no output schema, the description conveys scope, data source, and the shape of the answer (cost comparison against taxi/bus). It leaves the return structure (per-lot breakdown vs single cheapest pick) to inference, but nothing critical to invoking it 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 coverage is 100%, with both parameters documented including units, defaults, and bounds, so the schema does the heavy lifting. The description only restates the concepts ('trip length and number of people') plus a round-trip framing that isn't in the schema, which is a marginal addition. Baseline 3 is appropriate.

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 verb and resource: compare trip costs across every MSY parking lot against taxi and bus alternatives, scoped to a given trip length and party size. An agent can distinguish it from siblings like find_parking or park_and_ride without opening the schema.

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?

Gives concrete triggering questions ('cheapest parking at MSY for 4 days', 'should I park or take a cab') that make the intended use case unambiguous. It stops short of naming which sibling to use for adjacent needs (e.g., check_parking or find_parking), so no explicit exclusions.

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