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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds substantial behavioral context beyond them: the 5-year default window, that access is open without a key, that serie=True changes the return shape, that an unkeyed call returns only a 30-session sample with an `aviso`, and that a total-return methodology is applied. This is exactly the kind of access/limits disclosure the annotations do not carry.

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?

Dense but front-loaded: the core behavior comes first, then the serie/codigo modes, then the methodology caveat. Backticks isolate parameter names effectively. It is somewhat run-on and packs several modes into long sentences, but for a 7-parameter tool with three distinct modes nothing feels wasted.

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?

No output schema exists, and the description compensates by describing the returned fields (`data`, `fechamento`), the `aviso` on sampled responses, and the metric set (return, drawdown, volatility, moving-average crossover). Given seven parameters and multiple modes, this is nearly complete; only the date-parameter semantics remain under-specified.

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?

With schema coverage at 0% across 7 parameters, the description must carry the load, and it does for the important ones: serie (changes output to daily closes), codigo (empty string lists indices and coverage; default IBOV), chave_api (determines sample vs full series), and the 21x100 moving-average pair. The de/ate date parameters are only implied through the period phrasing and their formats are never stated, so it misses full compensation.

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 names a specific resource (B3 market indices: IBOV, IFIX, SMLL, IDIV, IBXX) and states concretely what it returns in each mode. An agent can tell this is the index-performance tool, distinct from siblings like precos, desempenho, or etf. It does not explicitly name a sibling it is not, so it falls short of a 5.

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 a use-case framing ("the benchmark to compare a stock or a strategy") and explains which modes exist (default, serie=True, codigo=""), which implies when to pick each. However it never states when NOT to use this tool or name an alternative sibling when another data source is more appropriate, so usage is only implied.

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