securitytrails_subdomainsEnumerate subdomains of . Returns the subdomain labels plus fully-qualified domains. Example: securitytrails_subdomains({ hostname: "github.com", _apiKey: "your-key" })
| Name | Required | Description | Default |
|---|---|---|---|
| _apiKey | Yes | SecurityTrails API key | |
| hostname | Yes | Apex domain / hostname to enumerate, e.g. "github.com" |
Changes observed during successful MCP inspections.
Input schema / examplesAdded value: +[
+ {
+ "_apiKey": "your-securitytrails-api-key",
+ "hostname": "github.com"
+ }
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare idempotent and read-only behavior. The description adds useful context about the return format (subdomain labels plus fully-qualified domains), which is beyond what annotations provide.
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 sentences, no wasted words. The verb and resource are front-loaded, and the example is compact.
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 enumeration tool with robust annotations, the description is complete: it states purpose, input, and output format. No output schema exists, so the description's mention of return value is sufficient.
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%, so the schema already describes both parameters. The description adds a concrete usage example showing parameter values, which aids understanding 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 the verb 'Enumerate' and resource 'subdomains of <hostname>'. It distinguishes from sibling tools like securitytrails_domain and securitytrails_whois by focusing specifically on subdomain enumeration.
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?
No guidance is given on when to use this tool versus alternatives such as securitytrails_dns_history or securitytrails_domain. The agent must infer usage from the tool name alone.
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.