Discover subdomains of a domain from public Certificate Transparency logs (crt.sh). Useful for mapping a company's public surface (app., api., staging., etc.). Best-effort: crt.sh can be slow; returns a note if unavailable.
| Name | Required | Description | Default |
|---|---|---|---|
| domain | Yes | Registrable domain, e.g. stripe.com |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description must disclose behavioral traits. It mentions best-effort, source (crt.sh), potential slowness, and a note on unavailability. However, it does not mention rate limits, return format, or whether it respects robots.txt. This is adequate but not exhaustive.
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?
Three sentences, each essential. First sentence states core action and source, second gives use case, third sets expectations. No redundancy, no fluff.
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 tool with one parameter and no output schema, the description covers purpose, usage context, and limitations. It does not detail the return format (e.g., list of subdomains), but the mention of 'returns a note if unavailable' implies some structure. Overall, it is largely complete.
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 coverage is 100% with one well-described parameter. The description adds value by specifying 'registrable domain' and giving an example (stripe.com), helping the agent understand the expected input format beyond the schema.
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 'Discover subdomains of a domain from public Certificate Transparency logs (crt.sh)', which is a specific verb+resource+source. It also gives a use case (mapping public surface) and examples, distinguishing it from sibling tools like dns_lookup or tech_stack.
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?
It says 'Useful for mapping a company's public surface', providing clear context on when to use. It also notes best-effort behavior and potential slowness. However, it does not explicitly state when not to use or compare to alternatives like dns_lookup.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Each tool targets a distinct aspect of domain intelligence: DNS records, registration, combined report, email authentication, subdomains, and tech stack. There is no overlap; even the domain_report is a composite that doesn't conflict with individual tools.
All names use snake_case and are descriptive, but the pattern varies: some are noun_verb (dns_lookup), noun_noun (domain_intel, domain_report, email_deliverability, tech_stack), or single noun (subdomains). This is mostly consistent but not perfectly uniform.
Six tools is an ideal scope for a domain intelligence server. Each tool adds unique value without redundancy, covering registration, DNS, email, subdomains, tech stack, plus a combined report.
The tool set provides comprehensive coverage of domain intelligence: registration details, DNS records, subdomain discovery, email deliverability, and website technology fingerprinting. No obvious missing capabilities for typical lead qualification or research workflows.