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

With no annotations, the description carries the burden: it does disclose anonymous callability and that results are an aggregated summary excluding individual stores, which is genuine behavioral context. It says nothing about result size, ordering, or whether empty brands are included.

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?

Two short, front-loaded clauses with the answer level stated immediately; the trailing '本体: vendor → Action: brands' is internal taxonomy boilerplate that adds little for an agent but costs only a few tokens.

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 zero-parameter, no-output-schema read tool, the description plus the aggregation note is enough to call it correctly. Only the exact shape of the returned brand/city mapping is left unstated.

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 there is nothing to document and the baseline is 4. The description correctly implies no filtering input is needed.

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?

States a specific verb+resource: query which cities each health-check brand covers, and clarifies the aggregation level (brand-level summary, not specific stores). This separates it from a store-level listing, though it never names the sibling vendor_list it is closest to.

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?

Usage is only implied by the negative constraint '不返回具体门店' — an agent can infer this is for brand-level coverage rather than store lookup, but there is no explicit when-to-use/when-not and no named alternative such as vendor_list.

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