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

Annotations already establish readOnlyHint=true, idempotentHint=true, destructiveHint=false and a closed-world scope, so the safety profile is fully covered. The description contributes only the fact that results are per-shipment (an order can have multiple) — useful granularity, but it does not cover error behavior for unknown order_ids or the empty-shipment case.

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?

One tight sentence with no filler, and the returned fields are front-loaded. The comma-heavy fragment structure ('...of an order, and the delivery estimate') slightly obscures that this is an action, but there is no wasted text.

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?

Given a single fully documented required parameter, an output schema covering return values, and annotations covering safety semantics, the description is nearly complete for this simple retrieval tool. Only error/empty-result behavior is left unstated.

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?

With a single parameter at 100% schema description coverage ('order_id returned by purchase'), the schema carries the semantic load, so baseline 3 applies. The description text never mentions order_id or how to source it, adding nothing beyond the schema.

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 names the exact payload (carrier, tracking number, tracking link, delivery estimate) scoped to each shipment of an order, which is specific enough to distinguish it from get_order or purchase. It lacks an explicit verb ('Get/Retrieve'), reading as a bare noun phrase, but the resource and scope are unambiguous.

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?

There is no statement of when to use this tool versus siblings like get_order (order status/details) or cancel_order. An agent must infer that this is the post-purchase tracking lookup; no prerequisites, alternatives, or exclusions are given.

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