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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior. The description's added value is mostly output-semantics guidance (what each price field means), which is real but framed as a correction. It discloses nothing about ordering, pagination, or empty-result behavior.

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?

Front-loaded with the trigger condition, but over half the text is field-definition and a negative instruction ('Never describe...') that reads as output-format policing rather than tool-selection help. It is not padded with filler, but the emphasis is misplaced for a definition whose job is invocation.

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 single-param read tool with full annotations, the description plus schema is nearly sufficient to call it correctly. However, it never mentions the sibling get_sale_offers it is easily confused with, and with no output schema the field explanations only partially substitute for return-structure documentation.

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% (zip is documented as a 5-digit US ZIP), so the schema carries parameter meaning. The description names no parameter and adds no format or constraint detail, so baseline 3 applies.

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 (offers) and resource (Rental containers) scoped to a ZIP, and the trigger condition (user asks what's offered to a ZIP). It does not explicitly distinguish itself from siblings like get_sale_offers or check_delivery, which it could have done given the naming overlap.

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?

Gives a clear triggering condition ('when the user asks what Rental containers WCS offers to a ZIP'), which implies when not to use it (sale offers go elsewhere). It names no alternative tool explicitly, so it stops short of full when/when-not routing.

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