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

Annotations declare readOnlyHint=true and destructiveHint=false, and the description adds valuable behavioral context: cost structure (2/6/10 credits), the quote-confirmation flow for size 1000, free repeats for known-empty lookups, and the return shape (top limit pages plus total_count). This goes beyond what annotations alone provide.

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 description is compact and front-loaded with the core purpose, followed by cost and return details. Every sentence adds useful information. Slight redundancy with the schema (cost is mentioned in both description and size parameter description) but not enough to hurt clarity.

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 lookup tool with 6 parameters and no output schema, the description covers the essential behavioral aspects: cost, confirmation flow, defaults, and return shape. It doesn't describe pagination beyond limit, but the limit parameter and total_count return value make that reasonably clear. The country default chain is well explained.

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 all 6 parameters. The description adds value by explaining the cost implications of size, the confirmation requirement for size 1000, and the default behavior for limit and country. It doesn't deeply explain order_by semantics, but the enum values are self-explanatory.

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 clearly states the tool's purpose: 'A domain's best-performing pages' with specific metrics (estimated traffic, traffic value, ranking keywords, average position, position split). It distinguishes itself from sibling tools like domain_overview and domain_keywords by focusing on pages rather than overall domain metrics or keyword-level data.

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?

The description provides clear context on when to use this tool (for top pages of a domain) and includes important usage details like cost tiers, confirmation flow for size 1000, and free repeats for known-empty lookups. It doesn't explicitly name alternative tools for when NOT to use it, but the sibling list and the page-specific focus make the use case clear.

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