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

There are no annotations, so the description carries the behavioral disclosure burden. It reveals the data provenance (official Prefectura Naval data), the exact rivers covered, the port-by-port granularity, and the temporal scope ('hoy'). It does not describe response structure or failure modes, but for a zero-parameter read the key behavior is communicated.

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 sentence with no filler. The main subject, river heights, is front-loaded, followed by the key qualifiers: which rivers, temporal scope, source, and daily variation.

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 parameterless retrieval, the description is largely complete: it names the source, the rivers, the granularity, and the temporal scope. It could additionally state exact units or response format, but those are minor omissions for such a low-complexity tool.

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 tool has zero parameters and the schema fully covers that, so the baseline 4 applies. The description adds useful context about what data the no-argument call returns, even though there are no parameters to explain.

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: today's river heights for the Paraná, Paraguay, and Uruguay rivers, port by port, with daily variation. It also cites the official source, Prefectura Naval, which makes the purpose unmistakable and clearly distinct from the unrelated sibling tools.

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?

The description does not explicitly state when to use this tool versus alternatives, but the domain is specific enough that an agent can infer it is for river-height queries. None of the sibling tools appear to compete for the same domain, so the lack of explicit exclusion guidance is a minor gap.

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