subfinder subdomain search

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

Annotations already cover safety (readOnlyHint, idempotentHint, non-destructive). The description adds useful behavioral context by stating that results come from passive sources and that the return includes reporting sources, but it does not disclose additional traits like rate limits or the default fast source set beyond what the schema already mentions.

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?

Two compact sentences with no filler. The core action and scope come first, and the return behavior is stated in the second sentence. Every sentence earns its place.

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 simple read-only discovery tool with annotated safety and fully documented parameters, the description is complete enough. It explains the return value even though there is no output schema. It could add a note about when to prefer sibling tools, but that gap is minor.

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 parameters domain, timeout, and all_sources are already fully documented. The description adds no additional parameter-level meaning, so the baseline score of 3 is appropriate.

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 and resource: 'Find subdomains of a domain in passive sources'. It also scopes the tool explicitly to passive discovery (certificate logs, DNS datasets) and names subfinder, making its role distinct from active or broad sibling tools like dnsrecon_domain_scan.

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 passive-source wording gives clear context for when to use this tool: passive subdomain discovery. It does not explicitly state when not to use it or name an alternative sibling, but the intended use is implied strongly enough.

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