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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond that by enumerating the returned report contents (weekly variation, fullest/emptiest reservoirs, year-over-year and 10-year comparisons), which sets expectations for the response.

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 information-dense sentence that front-loads the core purpose (total and fill percentage) before listing supplementary returns. It is grammatically heavy but contains no filler clauses that could be dropped.

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, the description correctly carries the burden of describing return values and does so thoroughly. Only 2 parameters (0 required), and the scope/name logic is adequately conveyed, leaving little an agent needs that isn't present.

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 coverage is only 50%: 'nombre' is documented in the schema while 'ambito' has an enum but no description. The description compensates partially by naming the four scopes (España, comunidad autónoma, provincia, cuenca hidrográfica) that map to the 'ambito' enum and by implying 'nombre' identifies the chosen region, reaching the baseline for the coverage gap.

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 resource and scope: aggregate reservoir water (total volume, fill percentage) for Spain or a region/province/basin. An agent can tell this is a summary/aggregate tool. However, it never references the sibling tools (buscar_embalses, estado_embalse, historico_embalse), so differentiation is left to inference.

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 says what the tool covers but never states when to use it versus the sibling search/status/history tools. No exclusions, prerequisites, or alternative-selection guidance are given; usage is only implied by the summary nature of the output.

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