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

Annotations already declare the tool as read-only and non-destructive. The description adds meaningful behavioral context beyond these: it states the tool is 'Claude grounded by web search' (indicating reliance on external web data and potential variability in results) and mentions '0 credits' (cost-free operation). It also clarifies the behavior of different modes (excluding or including the searched company). There is no contradiction with annotations, and the additional details are useful for the agent.

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 single, compact sentence that front-loads the core purpose ('Discover a brand's competitor / similar / adjacent brands from its domain') and then packs the mode explanations and cost note efficiently. It is appropriately sized, with no fluff or redundancy. Slight density from the inline mode listing does not detract from readability, making it well structured for quick parsing.

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 tool with only two parameters (one required, one optional enum) and no output schema, the description covers the essential operational aspects: purpose, modes, cost, and grounding. It does not describe the return format or typical output shape, but given the straightforward discovery nature of the tool and the absence of an output schema, the description is fairly complete. An agent can call it correctly without missing critical information.

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%; both domain and mode are already described in the input schema with clear descriptions and an enum for mode. The description repeats the mode meanings ('competitors' excludes the searched company, 'inspiration' includes it) but adds no new semantic detail beyond what the schema already provides. Since the schema carries the full burden, a baseline of 3 is appropriate; the description does not meaningfully enhance parameter understanding.

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 function: discovering a brand's competitor, similar, or adjacent brands from a domain, with an explicit grounding method (Claude grounded by web search). It differentiates the three modes (competitors, inspiration, company), making the purpose specific and unambiguous. However, it does not explicitly contrast itself with sibling tools like competitor_teardown or pull_competitor_ads, so it lacks direct sibling differentiation.

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 clear context on when to use the tool: when the agent needs to discover a brand's competitors or similar brands from a domain. It also explains the three modes and their behavioral differences (e.g., competitors excludes the searched company, inspiration includes it). It does not explicitly mention alternative tools or when not to use this tool, but the mode descriptions give practical usage guidance, meeting the 'clear context, no exclusions' criterion.

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