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

Annotations already cover safety (readOnlyHint, idempotentHint, destructiveHint=false, closed-world), so the bar is lower. The description adds genuine behavioral value beyond that: it discloses the return payload (earliest/latest estimate, warnings for PO box/hotel/holiday window, suggested action), which tells the agent how to act on the result.

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, and the core question is front-loaded ahead of the return-value summary. Every clause carries information.

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 an output schema present the description needn't detail return values, yet it still summarizes them usefully; annotations carry the safety profile and the schema carries parameter detail. Nothing an agent needs to select or invoke this read-only check 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 description coverage is 100%, so all five parameters are already documented — including the locale caveat that it affects language only. The description restates country/city/date/gift but adds no format or constraint detail beyond the schema, so the baseline 3 applies. Locale is not mentioned at all in the prose.

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 (check delivery feasibility) and enumerates the narrowing dimensions — country, city, date, gift — so the scope is unambiguous. None of the siblings (create_checkout, get_order_status, search_gifts, etc.) overlap this function, so no explicit sibling differentiation is needed.

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 framing question establishes when to reach for this tool (before promising a delivery) and the optional qualifiers show which context improves the answer. There is no explicit 'when not to use' or named alternative, so it stops short of a 5.

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