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

Beyond the annotations, the description discloses critical behavioral limitations: it returns a CT sample (not a full inventory), the count is a lower bound, hosts without publicly-logged certificates are invisible, and results include a per-source coverage record. This goes well beyond the read-only hint and helps the agent set correct expectations.

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 first sentence is concise and action-oriented, but the second sentence is dense with caveats and may be slightly long. Still, every clause contributes value by explaining the sampling limitation, making it a well-structured but not perfectly minimal description.

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, the description explains key aspects of the return value (sample nature, lower bound, coverage record), which is essential for an agent. It doesn't fully detail the output structure, but given the tool's simplicity and the schema covering parameters, this is adequate for a discovery 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 input schema has 100% description coverage for all three parameters (domain, format, force_refresh), so the baseline is established. The description does not add parameter-specific semantics beyond the schema, but it does hint at the sampled nature of results, which indirectly informs how to interpret the domain parameter. With full schema coverage, this is acceptable.

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 opens with a specific verb-resource pair ('Find subdomains of a domain') and identifies the method (Certificate Transparency logs), which clearly establishes what the tool does. It also distinguishes itself from sibling tools like check_dnssec or scan_domain by focusing on CT-based discovery and the associated shadow IT/forgotten services use case.

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 implies usage for discovering subdomains via CT logs but does not explicitly state when to prefer this tool over alternatives such as discover_brand_domains or check_subdomain_takeover. It provides no exclusion criteria or when-not-to-use guidance, leaving the agent to infer the appropriate context.

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