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

Annotations already cover readOnlyHint and openWorldHint, so the safety profile is set. The description adds meaningful context beyond that: the department-scoping rule, the not-found error for out-of-scope certs, and the fact that login-gated data is unavailable through this tool. It stops short of 5 only because it doesn't detail rate limits or response shape beyond the field list.

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 purpose and scope, then the parameter meaning, then exclusions. The long enumerations of returned fields are somewhat dense but each clause is informative; there is little pure 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?

For a single-parameter lookup with an output schema present, the description covers what the tool does, the exact input meaning, the scope boundary, and the not-found failure mode. Nothing an agent needs to invoke it correctly is missing.

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 0% and the schema only types CertNumber as a bare string, so the description carries the burden and does so: it defines it as the numeric certification number printed on the graded item's label, telling the agent exactly what value to supply. That is more than 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?

States a specific verb (lookup) and resource (PSA's own public Cert Verification record) plus the exact scope (one certification number). It enumerates the returned fields and clarifies it is scoped to the trading-card department, so an agent can distinguish it from sibling PSA tools like psa_cardfacts_checklist or psa_price_guide_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?

Clearly states when it applies (trading-card department cert numbers) and the failure mode (cert numbers from other divisions return not-found), and explicitly rules out PSA's Population Report and Auction Prices Realized because they require login. It does not name an alternative sibling tool, so it stops short of a 5.

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