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

With no annotations, the description carries the full burden and does disclose useful behavior: the date default and the non-business-day fallback to the previous date. It still omits the return shape (how the two rates are presented), pagination, auth, and rate limits, leaving meaningful behavioral gaps for a data tool.

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 front-loaded sentence giving the resource first, then the rate variants, then the date behavior. No wasted words, though the parenthetical default/fallback clause packs several behaviors into one dense line.

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 annotations and no output schema exist, so the description is the sole source. It adequately identifies the resource and date handling but does not describe the structure of the two returned rates or error behavior when no data exists, leaving it only minimally complete.

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 single 'fecha' parameter has 0% schema description coverage (only a regex pattern), so the description must compensate. It does so by defining the default value (today) and the fallback semantics for non-business days, adding real meaning beyond the bare pattern in the 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?

States a specific verb implicit (retrieval of 'tipo de cambio') and resource (dólar BCRA), naming both the wholesale (mayorista, Com. A 3500) and retail (minorista promedio vendedor) rates. It is distinguishable from siblings like uy_cotizaciones (Uruguay) or ar_tasas, but does not explicitly name any sibling to route between.

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?

Provides implicit usage context by explaining the default (hoy) and the fallback to the last prior date if the requested day is not a business day. However, it offers no explicit when-to-use vs. when-not guidance and never points to alternative sibling tools such as ar_feriado or dias_habiles for date resolution.

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