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

Annotations already cover read-only, idempotent, non-destructive and closed-world, so the description's real contribution is the access model (free vs. key-gated, free vs. Pro tier) and the returned comparison fields — both genuinely additive. It says nothing about behavior with tickers that never restated, error responses, or pagination, keeping it out of 5 territory.

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?

Front-loads what the tool returns before the access-tier details, and every sentence carries information. Slightly dense, stacking output shape, product differentiator and monetization rules into three sentences, but there is no filler.

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 output schema, the description takes on the burden of describing the return columns (ano, conta CVM, valor antigo × novo, variação) and does so competently, alongside the auth prerequisites. Remaining gaps are edge-case behavior — empty results for non-restating companies, ticker format, error handling — which are secondary for a simple two-parameter read.

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 coverage is 0%, so the description must carry parameter meaning. It does reference both parameters in prose — 'ticker' via the WEGE3/other-tickers example and 'chave_api' as a free-or-Pro key — but adds no ticker format (e.g. WEGE3 vs WEGE3.SA), no guidance on obtaining a key, and no explanation of why chave_api defaults to an empty string.

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 concrete resource with unusual precision: restated (republished) financial statements, with the exact shape of the comparison (year, CVM account, old vs. new value, variation). The 'reapresentação registrada, nunca corrigida em silêncio' framing implicitly separates it from tools that surface only current figures, but no sibling (e.g. fatos_contabeis, trimestres) is named, so full sibling discrimination isn't explicit.

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?

Gives clear calling context that an agent would otherwise have to discover by failure: WEGE3 works without a key, other tickers require chave_api, and per-version restatements are gated behind the key. It stops short of naming alternatives or stating when NOT to use it (e.g. when the caller just wants current-period statements).

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