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

With no annotations provided, the description carries the full burden and does well: it discloses deduplication, inline per-domain error handling, the exact price ($0.01 USDC via x402) and the condition for charging (only if at least one domain succeeded). It doesn't cover authentication requirements beyond payment or rate limits, which are minor gaps given the tool's scope.

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 three tight sentences, front-loaded with the core purpose and scope, then error behavior, then pricing. Every sentence adds distinct value with no fluff.

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?

The tool has no output schema and no annotations, so the description must carry significant weight. It adequately covers what is returned (same as domain_lookup), error handling, pricing, and limits, but it doesn't describe the return format in more detail beyond the sibling reference or explain payment timing—both are relatively minor given the tool's complexity.

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 documents the single parameter with 100% coverage (1-10 domains, min/max). The description adds meaningful semantics beyond the schema by noting that domains are deduplicated, which affects how the array is processed and is not captured 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?

The description states a specific verb (bulk domain lookup) and resource (DNS + RDAP registration report) and explicitly distinguishes it from the sibling domain_lookup by being for up to 10 domains in one call. An agent can immediately tell this is the batch version of domain_lookup.

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 gives a clear context for use: when you need the same report for multiple domains (up to 10) in one call, and it references the single-domain alternative domain_lookup. However, it does not explicitly state when not to use this tool (e.g., for a single domain) or list exclusions, so it falls short of the top score.

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