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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false, and destructiveHint=false, so the safety profile is covered. The description adds plan-gated authorization context (Creator Max / agency Pro, Scale, Enterprise), which is real behavioral information beyond the annotations; it does not, however, mention rate limits or whether counts vary by plan.

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?

A single front-loaded sentence stating the returned facets first, then the access prerequisite. Every clause earns its place and nothing is padded.

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 an output schema documenting the returned filter values and counts, annotations covering the safety profile, and zero parameters, the description only needs to convey purpose and access gating — both of which it does. Nothing required for correct invocation is missing.

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 tool takes zero parameters, so per the rubric the baseline is 4. The description correctly introduces no parameter information it doesn't need.

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?

Specific verb (Return) plus specific resource (the valid industries, countries, and categories accepted as Find sponsors search filters) and scope (with directory counts). It is clearly distinguishable from sibling search tools like sponsor_search_brands, which consume these values rather than enumerate them.

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 states an eligibility prerequisite ('Requires Creator Max or an agency Pro, Scale, or Enterprise plan'), which is useful context, but never says when to call this versus the sibling search tools or that it should be invoked to discover valid filter values before searching. Usage is only implied.

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