check_lookalikes

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

Annotations already declare read-only, idempotent and open-world, but the description adds substantial behavioral context the annotations cannot: DNS-only scope, that results are facts and never a verdict, that unregistered names are never listed, that unchecked names count as unknown (with complete=false), and that same_infra indicates defensive registration.

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 usage trigger is front-loaded and every clause carries actionable content (relay-as-facts rule, unknown semantics, next_steps printing instruction). It is dense and slightly run-on, packing return-field and output-formatting guidance into one long block rather than separating them, but there is little waste.

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?

With no output schema, the description carries the return-shape burden and does so: it describes the counts, the ten-name cap, per-name fields (variant kind, mail acceptance, same_infra), the complete flag, and how to render next_steps. An agent has everything needed to call and present results correctly.

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 description coverage is 100% for the single domain parameter, and the schema already documents accepted forms (bare names, subdomains, punycode normalization). The description adds nothing about the parameter, so the baseline of 3 applies.

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 states a specific verb and resource — it checks the closest DNS variants of a domain for lookalike/typosquat/impersonation use — and enumerates what it returns (resolving count, mail-accepting count, up to ten names). It does not, however, distinguish itself from the similarly named sibling get_lookalikes, which an agent could easily confuse it with.

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 gives a concrete triggering condition: 'Use this when the user asks about lookalike, look-alike, typosquat or impersonation domains of their domain.' That is clear context for invocation, but there is no when-not guidance and no routing to the get_lookalikes sibling or to start_monitoring_signup beyond the next_steps mention.

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