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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so 'No network call' largely restates structured data. What the description does add beyond annotations is the substance of the response — the band boundaries, the EPA protection advice, and the NWS UV Alert rule — which is valuable because no output schema exists to convey it.

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 front-loaded sentence that leads with the core purpose, then the scale breakdown, then the extra outputs, ending with the no-network note. The inline parenthetical band list is dense but earns its place as the tool's core content; nothing reads as filler.

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 and a trivial one-parameter input, the description does the important work of telling the agent what it will get back (band label, EPA advice, NWS alert status) and that no network call occurs. It falls slightly short on return structure and on handling of values at or near the 25 maximum, but overall it is sufficient to call the tool correctly.

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% for the single parameter (number, 0–25, example 7), so the schema already carries the mechanics. The description adds interpretive meaning for that number by spelling out the band thresholds, which helps an agent understand what the input maps to, but it does not address the schema's 0–25 bounds or what happens outside the described 0–8+ bands.

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 action (interpret/explain) on a specific resource (a UV Index number) and enumerates the content returned: EPA scale bands, EPA protection advice, and the NWS UV Alert rule. That clearly separates it from the siblings get_uv_index_today and get_uv_index_hourly, which retrieve data rather than interpret a supplied value, though it never states that distinction outright.

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?

Usage is implied rather than stated: an agent can infer it should call this when it already holds a UV Index number and needs meaning or advice, and 'No network call' hints it is the offline alternative to the fetching siblings. There is no explicit when-to-use/when-not-to-use sentence or named alternative, so the routing is left to inference.

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