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

No annotations are provided, so the description carries the full burden. It discloses the output fields (Sunshine Score, temperatures, rain, UV index, sea temperature, and a verdict), which is helpful. However, it does not mention any limitations, potential errors (e.g., invalid destinations), or explicitly state that it is a read-only operation. The description is not misleading, but it lacks deeper behavioral context beyond the output summary.

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 description is concise and efficiently structured: two sentences. It front-loads the core purpose ('Side-by-side sunshine/climate comparison'), then elaborates on scope and output. Every sentence earns its place with no fluff or repetition of schema details.

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?

There is no output schema, but the description explicitly enumerates the return values (Sunshine Score, temperatures, rain, UV, sea temperature, verdict), which mitigates that gap. It also covers the optional month parameter and the range of destinations. It is not fully complete—it doesn't describe error behavior or data sources—but for a comparison tool with this simplicity, the key aspects are covered.

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 100%, so the parameters are already fully documented: destinations (array, min 2, max 5) and month (optional, omit for year-round). The description adds an example phrase but does not introduce new semantic meaning beyond what the schema provides. Thus, the baseline score of 3 is appropriate.

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 states the tool performs a side-by-side comparison of 2–5 destinations, focusing on sunshine/climate metrics. It distinguishes itself from sibling tools by emphasizing comparison (find_sunny_destinations searches for sunny places, get_destination_climate likely focuses on a single destination). The verb 'compare' and resource 'destinations' are specific and unambiguous.

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 offers clear context on when to use the tool: for comparing multiple destinations, either year-round or for a specific month, with an illustrative example ('Algarve or Crete in October?'). It does not explicitly name alternative tools or exclude them, but the comparative scope (2–5 destinations) inherently distinguishes it from siblings. It could benefit from an explicit 'use this when you need to compare multiple places' recommendation.

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