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

Annotations already declare readOnly, idempotent and closed-world, so safety is covered. The description still adds real value by disclosing the shape of the result (fixed set of 9 stores with address, phone, hours, Maps link), which tells the agent this is a small static lookup rather than a paginated query.

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 sentences, zero filler, with the scope constraint (9 stores, RS) front-loaded before the optional filter. Every clause carries information.

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 read-only, single optional-parameter lookup with no output schema, the description covers what it does and what comes back, which is close to sufficient. The only missing piece is the expected form of the city value.

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 0%, so the description must carry the single parameter — and it does state that "cidade" filters the list and is optional. However, it gives no format expectations (exact city name, accents, case sensitivity), so an agent cannot be sure how to phrase the value.

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 ("Lista") plus resource ("as 9 lojas físicas iHelpU no Rio Grande do Sul"), and it enumerates the returned fields (endereço, telefone, horário, link do Google Maps). The resource is unmistakably distinct from the phone/price siblings, so no agent could route to this tool by mistake.

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?

"Opcionalmente filtra por cidade" implies the two usage modes (full list vs. city-filtered), but there is no explicit when-to-use statement or exclusion. Because the siblings are unrelated (phones, purchase info, prices), the absence of alternative-routing guidance is a smaller gap, leaving usage only implied.

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