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Subdomain Enum

subdomain_enum
Read-onlyIdempotent

Discover subdomains to map an organization's attack surface using passive Certificate Transparency logs and DNS brute-force without active probing.

Instructions

Discover subdomains using passive methods: Certificate Transparency logs + DNS brute-force (no active probing). Use to map organization's attack surface; non-intrusive. Response carries next_calls — capped at 5 ssl_check hints (one per first-five subdomain) so triage scales to large enumerations without token bloat; pull tail entries by name when needed. Free: 30/hr, Pro: 500/hr. Returns {domain, count, subdomains, sources, found_via_wordlist, found_via_crtsh, crtsh_status, warnings, summary, next_calls}. Always check crtsh_status: 'ok' means the CT lookup completed (so a low count is real); 'timeout' / 'rate_limited' / 'unavailable' / 'error' means CT logs did not respond and the count is wordlist-only — the actual attack surface is likely larger, retry later or surface the limitation to the user.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
domainYesRoot domain to enumerate subdomains for (e.g. 'example.com', 'tesla.com')

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior5/5

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

Annotations (readOnlyHint, openWorldHint, idempotentHint, destructiveHint=false) are complemented by detailed behavioral info: next_calls capped at 5, rate limits (Free/Pro), and crtsh_status interpretation. No contradictions; adds significant context beyond annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is relatively long but well-structured: purpose first, then output schema fields, usage notes. Each sentence provides value; minor redundancy in method description but overall efficient.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given one parameter, rich output schema, and annotations, the description is fully comprehensive. It covers pagination, rate limits, result interpretation, and fallback behavior, leaving no gaps.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% with one parameter (domain) well-described. The description adds example values but does not significantly enhance beyond schema; baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool discovers subdomains using passive methods (CT logs + DNS brute-force), providing a specific verb and resource. It distinguishes from siblings by specifying the passive, non-intrusive method.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly says 'Use to map organization's attack surface; non-intrusive' and provides guidance on interpreting crtsh_status. However, it does not explicitly state when not to use it or alternative tools, though no direct sibling exists.

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

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