Enumerate subdomains

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

Even though annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior, the description adds substantial behavioral context: the cost model (one API query per call, each page separately billed) and the invariant that responses always include `total_count` and `has_more` so truncation is never hidden. These details go beyond what the annotations convey and help the agent plan efficient calls.

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 sentences, each with a distinct purpose: what the tool does, how to use it efficiently, and what to expect from the response. There is no filler and no redundancy with the schema.

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?

Given the tool has a 6-parameter schema with 100% description coverage, an output schema, and safety-relevant annotations, the description covers the non-obvious operational details (billing, pagination, truncation detection) that an agent needs. Nothing required for correct invocation 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 baseline is 3. The description adds meaning beyond the schema by explaining the billing trade-off between `limit` and `offset` and by telling the agent that `total_count` and `has_more` are always present, which informs parameter choices. It does not repeat each parameter's schema description.

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 ('List') and resource ('known subdomains of a domain') and specifies the output as 'fully-qualified hostnames, ready to feed into resolution or scanning.' This clearly distinguishes it from sibling tools like securitytrails_dns_history or securitytrails_domain_details, which address different 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 for when to use the tool ('ready to feed into resolution or scanning') and gives concrete, actionable guidance: prefer a single high-limit call over paging with offset because each page is billed separately. It does not explicitly name alternatives or exclusions, but the usage direction is unambiguous.

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