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

Annotations already cover read-only, idempotent, and non-destructive behavior, so the description adds important context beyond them. It discloses that ITR publishes only 1T/2T/3T and that 4T is deliberately not derived, that banks and insurers receive only net margin and ROE, and that WEGE3 is free while others require `chave_api`. This is rich behavioral context without contradicting annotations.

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?

The description is multi-paragraph but front-loads the core definition and every sentence adds necessary context: usage guidance, 4T rationale, sector coverage limits, and auth requirements. Given the tool's complexity, the length is justified and there is no redundant 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 and minimal schema descriptions, the description carries the full burden and succeeds. It covers what data is returned, when to use the tool, why 4T is excluded, sector-specific limitations, and authentication needs. An agent has enough to invoke it correctly.

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 compensate. It explains the `chave_api` condition well ('WEGE3 gratuita; demais exigem chave_api') and implies `ticker` via 'de uma AÇÃO' and the WEGE3 example, but it never specifies ticker format or requiredness. Adequate but incomplete compensation for an undocumented schema.

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 and resource: a quarterly series for a stock, with ITR accounts, quarter price, and indicators. It distinguishes itself from the annual sibling by naming `indicadores_anuais` and explaining why the fourth quarter is absent. An agent can identify its purpose and scope immediately.

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?

It gives explicit conditions for use: questions about the current year or the most recent quarter, with examples like 'como foi o 2T'. It names the alternative tool (`indicadores_anuais`) for closed fiscal years and explains the data-source reason. No ambiguity remains about when to choose this over siblings.

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