Subdomain Discovery

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

The description goes beyond the annotations by disclosing that it is 'fully passive (no packets are sent to the target)' and that CT logs are public records. It also explains the flagging behavior for operational-looking names and wildcard certificates, plus mentions rate-limiting and read-only nature. This richly informs the agent of the tool's runtime behavior.

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 moderately long but every sentence serves a purpose: it states the core action, explains the passive method, describes output flags, gives usage context, points to alternatives, and lists return values. It is well-structured and front-loaded with the primary purpose, so it remains concise despite the detail.

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 recon tool with one parameter, the description is complete: it covers input format, method, output contents, relationship to sibling tools, safety characteristics, and rate-limiting. There is no missing context that an agent would need to decide to call or interpret the results of this tool.

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 schema description covers 100% of the parameters, and the description adds extra semantic detail: the domain must be a 'registrable domain' without scheme or path, with an example ('example.com'). It also clarifies that subdomains found in CT logs for that domain are returned, so the parameter meaning is fully clear.

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 a specific verb and resource: 'Enumerate the subdomains of a domain from Certificate Transparency logs.' It also distinguishes itself from sibling tools by mentioning the passive CT-log method and by referencing dns_lookup and lookalike_domains as complementary next steps.

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 guidance is provided: 'Use this as the first recon step to map a domain's attack surface' and when to use alternatives: 'Use dns_lookup to check whether a discovered name still resolves, or lookalike_domains for typosquat variants.' This leaves no ambiguity about 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.