scan_domain

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It adds valuable context by stating the tool returns 'live results from public DNS records and TLS handshakes,' indicating a read-only, real-time scan. It also lists the specific security checks performed, giving the agent a clear model of behavior. However, it doesn't mention any potential side effects, rate limits, or edge cases.

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 efficiently structured in three sentences: the first states the core purpose and scope, the second provides usage triggers, and the third explains the method and return type. There is no redundant content, and each 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?

Given a simple single-parameter schema and no output schema, the description provides sufficient context for an agent to select and invoke the tool correctly. It covers the tool's purpose, when to use it, what it checks, how it works, and what it returns. This is complete for the tool's complexity and complements the sibling tools effectively.

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 schema already fully describes the 'domain' parameter with 100% coverage, including an example and constraint ('Do not include a scheme or path'). The description adds no new semantic detail beyond the schema, so the baseline 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 clearly states the tool's purpose with a specific verb ('Check') and resource ('a domain's full security posture'), and enumerates concrete components (SPF, DKIM, DMARC, MTA-STS, TLS, HTTP headers). It distinguishes itself from sibling tools like check_tls and analyse_spf by offering a comprehensive security review rather than a focused check.

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 explicitly states when to use the tool: 'Use this whenever asked whether a domain is configured securely, whether it can be spoofed, or to review a domain's email or web security.' This gives clear context, but it does not explicitly mention when to choose the specialized siblings (check_tls, analyse_spf) instead, so it lacks exclusionary guidance.

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