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 covered. The description adds real value beyond that by disclosing the response shape (per-service send-by date, days left, on-time flag) and the derived 'slowest cheapest service still on time' output, which annotations cannot convey.

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 purpose and output are front-loaded in the first clause, with destination formats following as supporting detail. It is a single dense sentence that stays on topic, though the long enumeration of destination examples makes it slightly heavy.

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?

With no output schema, the description carries the burden of explaining return values and does so adequately (per-service send-by dates, days left, on-time status, recommended slowest-cheapest option). Combined with full schema coverage and rich annotations, an agent has enough to call and interpret it correctly.

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, but the description goes further by enumerating the accepted destination forms (lower48, state/territory, country, USPS region, APO/FPO/DPO ZIP with an example) that the schema only vaguely calls 'Where the package goes'. It also restates the ship_date default, which is already in the schema, so it is not a full 5.

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 specific verb and resource ('For a ship date ... and a destination, lists each USPS service with its send-by date, days left and whether it is still on time'), so an agent knows exactly what it returns. It does not name the sibling tools (get_usps_holiday_shipping_deadlines, get_military_mail_deadline) to differentiate itself, which keeps it from a 5.

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?

Usage context is implied through the defaults ('default today, US Eastern') and the accepted destination forms, which tells the agent how to call it. There is no explicit when-to-use or when-not guidance relative to the two sibling deadline tools, so the agent must infer the distinction.

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