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

Annotations already declare readOnly/idempotent/non-destructive, yet the description adds genuinely new behavioral facts: the response shape with a ZIP (firm shipping cost and total) versus without one ("$67 plus shipping"), and the guarantee that the quoted rate is the same live carrier rate place_order will book. That consistency guarantee is exactly the kind of thing an agent cannot infer from schema or 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?

Three sentences, front-loaded with what the tool returns, then when to call it, then the ZIP branch. No filler, and the example output string conveys the degraded case faster than prose would.

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 return-value burden and does so: it names the four returned facts and shows both response shapes. Combined with the annotations covering safety and zero required parameters, an agent has everything needed to call 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; the description earns above that by explaining the consequence of supplying zip (a firm quote and total, tied to the booked rate) rather than just repeating its format. It says nothing about the state parameter beyond what the schema already states, which is its only gap.

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 a precisely scoped resource: pricing, shipping cost, lead time and allergens for one named product (edible photo macaron set). It also distinguishes itself from the ordering siblings by framing itself as the pre-order information call and by tying its shipping rate to the rate place_order books.

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?

"Call this before ordering so you can tell the person what it costs and what is in it" gives explicit timing and a downstream consumer of the result, and the ZIP/no-ZIP branch is spelled out. It stops short of naming when not to use it (e.g., for existing orders, where check_order applies) but the sibling routing is implicit and clear.

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