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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is covered. The description adds genuinely non-redundant behavior: the pricing model ($0.03 per successful call, failed calls free) and the exact shape of the returned review fields, which an agent needs for cost/benefit decisions.

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 purpose and returned fields, then the required input, then use cases, then cost — every sentence earns its place with no repetition or 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 read-only, idempotent lookup with an output schema and full schema coverage, the description supplies everything extra an agent needs: what the reviews contain, the required domain input, intended use cases, and the per-call price. Nothing material 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 100%, so the schema already documents domain, limit (default 20, max 40) and api_key. The description only reinforces the required 'domain' parameter and omits limit entirely; baseline 3 is appropriate when the schema carries the parameter burden.

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 ('Read a company's most recent Trustpilot reviews') and enumerates the returned fields (star rating, headline, review text, date, reply status, overall rating, count). Naming Trustpilot specifically differentiates it from the sibling business_reviews without needing the 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?

Gives concrete use cases ('vet a supplier or prospect', 'find a competitor's weak spots'), which tells the agent when this tool is the right choice. It stops short of naming alternatives or stating when not to use it (e.g. versus business_reviews for non-Trustpilot sources), so it falls just 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.