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

Annotations already declare readOnly, idempotent, non-destructive, non-open-world behavior, so the safety profile is covered. The description adds genuine value beyond them by disclosing the error case ('An unknown or closed listing is an error') and the return shape ('that one listing in full as text, with its url and structured details'). It stops short of describing pagination/size limits, but for a single-item fetch that is minor.

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-loads the when-to-use condition and the id prerequisite in the first sentence, then adds return and error behavior in order of importance. Slightly dense with the field enumeration, but every clause carries selection-relevant information and there is no filler.

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 only two well-documented parameters, full annotations, and an output schema covering return values, the description supplies exactly the missing pieces: trigger conditions, the no-search exclusion, and error semantics. Nothing an agent needs in order to call it correctly is absent.

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 description coverage is 100%, and the locale parameter is documented in unusual depth in the schema itself (BCP 47 format, site mapping, default). The description adds no parameter-level detail beyond the schema, so the baseline 3 is appropriate.

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 resource ('fetch' one Cerulean listing) and enumerates the fields returned (responsibilities, qualifications, skills, pay, benefits, languages), so an agent can tell exactly what this returns. It also explicitly carves out what it is not: 'It does not search.'

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 an explicit trigger condition ('when someone asks about one specific listing') plus the prerequisite ('its id or Cerulean URL is known') and an exclusion ('It does not search'), which implicitly routes search-style requests to the search sibling. Nothing about when to choose this is left to inference.

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