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

Annotations already establish the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false), and the description adds real value on top: values are verbatim as the site publishes them, with named source pages (Storage Units in Twin Falls page, rates table). It also preempts a likely wrong inference by stating availability is deliberately absent. It does not discuss staleness or update cadence, which would be the next useful disclosure.

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 core fact (two sizes with rent and deposit) is front-loaded, but the single sentence is heavily packed with parenthetical dimensions and two page references, making it dense to parse. The source-page attribution could be trimmed without losing selection-relevant information.

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?

An output schema exists, so return-value documentation is unnecessary, and the description still covers scope, data fidelity, and the availability exclusion. For a one-optional-parameter read tool with full annotations, that is nearly everything an agent needs. Only edge behavior (e.g., what is returned if a requested size is unavailable) is left implicit, though the enum largely forecloses it.

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% and the enum already enumerates both valid sizes with 'omit for both' documented in the property description. The description's 'Optionally one unit' merely restates optionality rather than adding meaning such as default behavior or ordering. Baseline 3 is appropriate when the schema carries the semantics.

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 concrete resource (the two unit sizes SJ Storage rents: 8x20 drive-up container, 12x30 powered indoor) plus the exact attributes returned (monthly rent, refundable deposit). It also separates itself from check_availability by stating availability is not included, so an agent can pick between them without opening either schema.

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 gives a clear usage boundary: this tool never reports whether a unit is open, and current availability lives on the linked availability page. That is an explicit when-not-to-use signal. It stops short of naming the sibling tool (check_availability) outright, leaving the agent to infer the handoff.

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