domain_fetch_subdomains

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

Annotations already declare readOnlyHint, destructiveHint, idempotentHint, and openWorldHint. The description adds valuable context: no side effects, caching with 24-hour TTL, circuit breaker mechanism, fallback sources, and response includes source field. No contradiction with annotations.

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 detailed but well-structured, front-loading the core purpose. It covers sources, caching, error handling, and fallback. Could be slightly shorter by consolidating some details, but overall concise given the amount of useful information.

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 description covers all critical aspects: data sources, caching, error handling, idempotency, and even a fallback action (report_feedback). With an output schema present, return value details are not needed. The description is thorough for this 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 has 100% coverage for the single parameter 'domain'. The description repeats the schema's description but adds no new semantic detail (e.g., format, validation). Baseline 3 is appropriate as schema does the heavy lifting.

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 enumerates subdomains via Certificate Transparency logs. It specifies the primary source (crt.sh) and fallback (RapidDNS), and the verb 'enumerate' is precise. This differentiates it from sibling tools like domain_fetch_dns_records.

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 explains when to use the tool (subdomain enumeration) and provides context on caching and fallback behavior. It also explicitly instructs to call report_feedback if the result doesn't serve the user's need. However, it lacks explicit 'when not to use' guidance.

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