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

With no annotations provided, the description carries full burden and does well by disclosing the public/no-API-key nature, batch limit of 50, and the return array's fields (availability, price, renewal price, registrar, buyUrl). It also notes performance characteristics. Missing only edge-case or error behavior, but for a read-only check tool, this is strong transparency.

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?

Two tightly written sentences front-load the most critical detail (no API key), then explain equivalence, batch size, return structure, and usage preference. No fluff, every sentence serves a purpose.

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?

Despite lacking an output schema and annotations, the description clearly enumerates the return fields and the single input parameter. It also covers when to use it versus alternatives, making it complete for an agent to select and invoke correctly.

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?

The input schema already covers 100% of parameter semantics with a clear type, maxItems restriction, and example format. The description adds limited new parameter information beyond confirming the 50-domain limit, so baseline of 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?

The description clearly states the tool checks up to 50 domains in one call, explicitly distinguishing it from the sibling check_domain_public. It specifies the action (check), resource (domains), and bulk scope, making the purpose unambiguous.

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?

Explicitly advises ALWAYS prefer this over multiple check_domain_public calls when multiple candidates exist, naming the alternative. Also justifies usage with 'faster + fewer rate-limit hits', providing clear context for when to choose this tool.

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