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

The description adds useful context beyond the annotations: the number is anonymized, requires an assigned courier, and expires at delivery end. With readOnlyHint and openWorldHint already present, this gives solid behavioral guidance, though it omits auth/rate-limit details.

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 front-loaded with the return value, followed by lifecycle constraints and the underlying Stuart endpoint. It is appropriately sized with no wasted sentences.

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 simple read-only lookup with fully described schema parameters, no output schema, and annotations covering safety, the description provides everything an agent needs: what it returns, when it works, and when it expires.

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 delivery_id parameter is already fully documented in the schema. The description reinforces the delivery context but does not add syntax or format details beyond what the schema provides.

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 states a specific resource—the courier's anonymized phone number—and ties it to a delivery. It is clear what is returned, though it does not explicitly differentiate itself from siblings, which are mostly job/delivery management tools.

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?

It clearly states the operating condition: only works once a courier is assigned and expires when the delivery ends. It does not name alternatives, but there is no obvious sibling alternative for this specific lookup.

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