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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds the key behavioral context: it reports cost, time, and a free-delivery boolean. However, it does not disclose return shape, units, or how the free-delivery threshold is determined, and there is no output schema to fill that gap.

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 a single sentence with no filler, front-loading the core outputs (delivery cost, time) and adding the free-delivery qualifier. It is appropriately concise for a simple tool.

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 tool, the description names the inputs and outputs concisely. However, there is no output schema, and the schema marks zero parameters as required; the description does not clarify whether city is mandatory or how the response is structured. This creates meaningful ambiguity for an agent deciding how to call the tool.

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 reinforces that city affects cost/time and order_total affects free-delivery eligibility, which is useful, but it adds no detail beyond what the schema already provides and does not clarify optionality or requiredness.

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 clearly states the tool's purpose: return delivery cost, delivery time, and free-delivery eligibility for a city/order. It is specific enough to distinguish it from typical product or availability tools, though it lacks an explicit verb like 'calculates' or 'returns'.

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 implies when to use this tool—whenever delivery cost, time, or free-delivery qualification is needed—but it does not explicitly state when not to use it or point to alternatives such as check_availability. The context is clear, but exclusions and sibling differentiation are missing.

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