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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuinely non-obvious context: the data is a snapshot ('as of the date we last saw it'), which warns about staleness, and it previews what the result actually contains. It does not cover the not-found case or lookup failures.

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?

Three short sentences with the core identification front-loaded and no filler. The middle sentence is slightly dense ('between them as of the date we last saw it'), but every clause carries 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?

For a one-parameter read-only lookup with no output schema, the description covers the identifier source, the shape of the result, and the freshness caveat. Nothing essential to calling 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 coverage is 0%, so the description must carry the parameter meaning — and it does, identifying the input as a grading report number and listing the labs that issue them, which tells an agent where to source the value. It does not mention the 5–20 character constraint documented in the schema.

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: 'Find a diamond by its grading report number', and enumerates the labs (GIA, IGI, HRD, GCAL) to clarify the identifier type. It also spells out the returned content (retailer listings, count, price range). It doesn't explicitly distinguish itself from the overlapping siblings price_check and get_diamond, so it stops short of a 5.

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?

'Useful to check whether a quoted price is fair' gives an implied usage context, which is more than nothing. However, with price_check and get_diamond as siblings, the description never says when to use this tool instead of those, nor what it does not cover (e.g., non-certified stones).

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