get_selic

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

With no annotations, the description carries the behavioral burden. It usefully explains that this is the current COPOM-defined target rate in percent per year, not historical data. However, it does not disclose whether the response is a bare number, whether it includes an effective date, or how frequently the value updates.

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?

A single, compact sentence with no filler. It front-loads the core meaning and every phrase adds value: current, SELIC, basic interest rate, unit, and source.

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 simple zero-parameter lookup of a current rate, the description is nearly self-contained: it tells the agent what value is returned, the unit, and the institutional source. It lacks return-shape details, but no output schema exists and the operation is simple, so the main missing piece is sibling-selection guidance.

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?

The input schema has zero parameters, so parameter documentation is unnecessary and the baseline 4 applies. The description adds relevant interpretive context by specifying that the value is a percentage per year and the SELIC target set by COPOM.

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 the exact resource (Meta SELIC atual), its unit (% ao ano), and source (COPOM), so the tool's purpose is unambiguous. It is a noun phrase rather than an explicit verb, but the resource is specific enough to distinguish it from siblings like get_cdi or get_ipca.

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?

There is no guidance about when to use this tool versus alternatives such as get_cdi, rentabilidade_vs_cdi, or get_serie_sgs. The description implies it returns the current SELIC target, but it gives no exclusions, prerequisites, or sibling-routing context.

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