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

With no annotations, the description carries the full behavioral burden. It usefully discloses the cost model ('Flat 5 points per successful run'), clarifying that billing occurs per run and only on success. However, it omits failure behavior (e.g., unknown CNPJ), auth requirements, and any rate-limit or caching notes.

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 compact sentences: the core lookup contract first, the cost note second. No filler, nothing redundant, and the highest-value information (what it fetches and by what key) is front-loaded.

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 single-record lookup with no output schema, enumerating the returned fields (name, status, registration date, address, legal form) plus the cost gives the agent enough to call it correctly. Minor gaps remain around not-found/error behavior and whether the URL form accepts any registry URL.

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?

Only one parameter with 100% schema description coverage, so the schema already documents the accepted format and example. The description restates 'registration number or registry URL' without adding syntax, normalization, or fallback guidance beyond the schema, so baseline 3 applies.

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 ('Get one company') plus precise resource (Brazil registry / CNPJ / Receita Federal) and the exact lookup key (registration number or registry URL). The phrasing 'one company' implicitly distinguishes this single-record lookup from the sibling run_br_companies_search, and the returned fields are enumerated.

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 tells the agent what input is accepted ('by registration number or registry URL'), which implies the usage context, but it never states when to prefer this over run_br_companies_search or what to do when only a name is known. Usage is inferred rather than prescribed.

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