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

With no annotations, the description carries the full behavioral burden, yet it only discloses one trait (CEP must be 8 digits). It is silent on the default situacao='ativa' filter that silently restricts results to active companies, on pagination semantics for limit/offset, and on permissions or result ordering — all material for correct invocation.

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 tight sentences with no filler, and the resource definition is front-loaded ahead of the use case. The inline '(8 digits)' detail earns its place as a format constraint; the parenthetical field list is dense but readable.

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?

Output schema exists, so return values need not be described, which the definition correctly omits. But for an 8-parameter tool with zero annotations and zero schema coverage, the description is only partially complete — pagination and the default active-status filter are unaddressed and could cause unexpected empty results.

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% across 8 parameters, so the description must compensate. It does cover five of them meaningfully (cep format, logradouro_contains as 'street text', numero, municipio, uf), but leaves limit, offset, and especially situacao — which defaults to 'ativa' with no explanation — completely undocumented.

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 states a specific verb+resource combination ('Establishments registered at one address') and names the exact scoping keys (CEP, street, number, municipio, uf). It distinguishes itself from generic siblings like search_companies and count_companies by narrowing to a single address, though it never names those siblings explicitly.

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 second sentence gives an implied use case ('Use it to find companies sharing an address'), which is clear enough for the primary scenario. However, it offers no when-not guidance and never explains how this differs from calling search_companies with an address filter, leaving the agent to infer the boundary.

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