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

With no annotations, the description carries the full burden and discloses important behavior: ranking order, monthly mean as the basis, and the exclusion of unmeasured beaches rather than ranking them as cold. This is valuable edge-case transparency beyond the schema.

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?

Three tight sentences: the first front-loads the core ranking behavior, the second anchors user intent, and the third discloses a key edge case. Every sentence earns its place with no redundancy.

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 read-only ranked-list tool, the description covers purpose, ranking logic, and an edge case. Without an output schema, it could be more complete by noting what fields each result contains, but the overall context is strong.

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 100%, so the schema already documents all parameters. The description adds no meaningful parameter-level information beyond reinforcing that month and mean sea temperature are central, which is already present 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?

The description clearly specifies a concrete operation: ranking beaches by mean sea temperature for a month, warmest first. The 'where can I swim in February?' question adds user intent, but the tool is not explicitly differentiated from siblings like sea_temperature_year.

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 'where can I swim in February?' framing provides a clear context for when to use this tool. It does not name alternatives or explain when not to use it, so it falls just short of full guidance.

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