check_lookalikes

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

Annotations declare readOnlyHint, openWorldHint, idempotentHint, and harmless, which cover the safety profile. The description adds that it detects 'active' domains, implying a live scan or freshness aspect, and mentions the type of registrations (by attackers). It does not detail output structure, but with annotations covering safety and the description adding scope, this is strong; minus one for not describing the return format or any rate limits.

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 a concise two-sentence block: first sentence defines the tool's function and use case, second sentence differentiates from key siblings. No filler; every 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?

The tool has a clear, narrow scope with a detailed input schema and an output schema (not shown but noted). The description covers the purpose, use context, and differentiation from two key siblings. It could mention what the output looks like (e.g., list of domains) but the output schema likely covers that, and the description is sufficient for a straightforward scan tool with rich annotations.

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%, so all parameters are well-described in the schema. The description adds a semantic focus on impersonation and 'active' domains, which reinforces the domain parameter's purpose, but does not add new syntax or format details beyond the schema. Baseline 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 detects active typosquat and lookalike/homoglyph domains that impersonate a brand, with specific examples of character-substitution and visual-confusion. It explicitly distinguishes from siblings check_shadow_domains and discover_brand_domains, meeting the high bar.

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 provides explicit when-to-use context: for detecting impersonation domains used in phishing. It names two specific sibling tools and how they differ, giving clear guidance on when not to use this tool (e.g., for TLD variants with auth gaps or legitimate portfolio discovery).

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