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

With no annotations, the description carries full burden and does well by disclosing rate limiting ('Rate-limited per IP') and the public/no-API-key nature. It also specifies the exact data returned, including a buyUrl, and instructs users to trust that URL. However, it does not mention error handling or behavior on invalid domains, so a perfect score is not warranted.

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 front-loaded with the most important fact ('PUBLIC, NO API KEY required'), then lists return values, usage rules, and the bulk alternative. Every sentence adds value; no fluff or repetition.

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 tool with no output schema, the description is complete: it lists all returned fields, provides clear usage direction, notes rate limiting, and points to a sibling tool for bulk checking. Nothing critical is missing for an agent to select and invoke this tool 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 single parameter 'domain' already has 100% schema description coverage with an example ('taskflow.app'). The tool description does not add additional parameter semantics beyond what the schema provides, so baseline 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's function: 'The one-stop tool for handing a user a domain decision' and enumerates exactly what it returns (availability, prices, registrar, buyUrl). It distinguishes itself from the sibling bulk tool by explicitly naming 'check_domains_public_bulk' for bulk checks.

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?

Explicit when-to-use guidance is given: 'Use this for EVERY candidate before recommending' and 'never invent URLs or prices, always trust the buyUrl this returns.' It also provides an alternative for bulk checks, saying 'For bulk checks (multiple domains in one call), use check_domains_public_bulk.'

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