get_water_balance

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

With no annotations, the description carries the full burden and does well: it declares units (millimetres), defines ET0 as et0_fao_evapotranspiration for well-watered reference grass, discloses the 366-day span limit and the archive/forecast merge behavior, and previews the returned artifacts. Gaps remain around coordinate system expectations and error/failure behavior, which prevents a 5.

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?

The core computation is front-loaded in sentence one, followed by usage constraints, output summary, and a concrete example — every element earns its place. It is on the longer side, but no sentence is redundant.

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?

An output schema exists, so the description only needs to orient the agent on what comes back — and it does (totals, weekly breakdowns, dryness note). Combined with the date/span constraints and example, an agent has enough to invoke it correctly; only coordinate-system specifics are left implicit.

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 description coverage is 0%, so the description must compensate — and it largely does: ISO YYYY-MM-DD date format, inclusivity, and the 366-day maximum are all documented, and the worked example (52.52, 13.41) conveys lat/lon order and approximate meaning. It stops short of stating WGS84/decimal-degree units or coordinate validity ranges, so not a 5.

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 opens with a specific verb-plus-computation: 'Calculate precipitation minus reference evapotranspiration.' This is a precise, distinguishable resource that an agent can easily tell apart from siblings like get_growing_degree_days or get_frost_risk without opening any schema.

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 clear applicability context: dates are inclusive, span at most 366 days, and past/future ranges are merged from archive and forecast data — which tells the agent when the tool works as expected. It does not explicitly exclude cases or name alternatives among the siblings, so it falls short of a 5.

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