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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is clear. The description adds behavioral context by mentioning 'parallel' processing and 'factual findings with source provenance', which tells the agent that output will be factual and sourced, and that the tool aggregates signals concurrently. No contradictions with annotations.

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 entire description is a single sentence (under 40 words) that front-loads the core action ('Investigate a domain') and efficiently lists signals and output characteristics. Every phrase earns its place with no redundancy.

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?

Despite the tool's multi-signal complexity, the description gives a high-level complete picture: it states the input domain, the types of lookups (DNS, TLS, RDAP, DNSSEC, SPF, DMARC), and the nature of results (factual with provenance). The presence of an output schema covers detailed return structures, so the description doesn't need to enumerate them.

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 provides only the parameter name 'url' with format uri; the description clarifies that it investigates a 'domain', which gives some semantic meaning. However, the tool does not explain whether the url parameter accepts a bare domain or requires a full URI scheme, and the mismatch between 'domain' and 'url' leaves ambiguity. Since the schema description coverage is 0%, the description provides limited compensation beyond the name.

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 investigates a domain using a specific set of signals (DNS, TLS certificate, RDAP, DNSSEC, SPF, DMARC) and emphasizes 'factual findings and source provenance'. This is a specific verb+resource+scope that differentiates it from siblings like web.email-auth or web.security-audit by naming the exact signal set and provenance feature.

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 implies usage when domain intelligence across multiple signals is needed, but it does not explicitly state when to prefer this tool over alternatives such as web.email-auth (which covers SPF/DMARC) or web.security-audit. There are no direct exclusions or alternative tool names, so usage context is only implied.

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