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

The annotations already mark the tool as read-only and idempotent, and the description adds essential behavioral detail: `search` is silently ignored and returns the entire unfiltered directory, and random *.myshopify.com domains indicate the query was not applied. This exposes a subtle failure mode the annotations cannot convey.

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 front-loaded with the purpose and each subsequent sentence earns its place by revealing a silent-ignore trap, a troubleshooting signal, and the alternative id lookup mode. It is detailed without being bloated.

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?

There is no output schema, so explaining return values is not required. The description covers the main failure mode, the filtering semantics, and the two invocation modes, making it sufficient for an agent to call the tool correctly despite the subtle `q` behavior.

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 describes `q` and `id`, but the description enriches both: `q` has a critical silent-ignore edge case, and `id` provides detail including `can_request_gift`. The `type` param is not explained, but its enum values are self-explanatory and schema coverage is moderate at 67%.

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 opens with a specific action and resource: 'Look up brands and their commission rates.' It clearly identifies the tool's domain and differentiates it from sibling search tools like split_search_links and split_search_products by focusing on brand lookup.

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 gives clear guidance on using `q` for brand filtering and `id` for fetching one brand's detail, including what `id` returns. It does not explicitly state when to prefer this tool over sibling search tools, so it lacks full alternative routing, but the usage context is clear.

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