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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuinely new behavioral context by disclosing that the response includes the caller's plan entitlements — an authorization/entitlement dimension the annotations say nothing about.

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 sentence with no padding, front-loaded with the primary resource (niches) before the secondary payloads. Slightly list-heavy but every clause identifies distinct returned content.

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 input parameters and no output schema, the description carries the burden of explaining the return shape, and it does enumerate the three payload categories (niches, signal types/filters, plan). Nothing critical is missing, though it could note whether results are paginated or static.

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?

Zero parameters, so the baseline is 4; there is nothing for the description to compensate for. It does usefully clarify that the payload includes consumable filter values rather than just labels.

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 names the specific content the tool returns: tracked niches, signal types and filter values, and the caller's plan entitlements. It implicitly distinguishes itself from search_signals by positioning itself as the reference/enumeration tool for that sibling's inputs, though it never states a verb like 'list' explicitly beyond the title.

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?

Mentioning that it exposes 'filter values search_signals accepts' hints that this should be consulted before calling search_signals, but the when-to-use relationship to check_store and lookup_brand is left unstated. Usage is implied rather than prescribed.

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