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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), but the description adds a real operational constraint: it 'Fetches every resort in the region, so it is limited to 40 resorts,' which warns the agent about truncation on large regions. It does not describe error behavior for an invalid region tag, so it stops short of full behavioral disclosure.

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?

Two sentences, no filler, with the core purpose and the scoping constraint front-loaded before the tag-source detail. Every clause earns its place.

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 single-parameter read-only tool with no output schema, the description covers what it returns ('each resort's count') and the 40-resort ceiling. It leaves the handling of an unrecognized region tag unspecified, which is a minor but real gap.

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% and the schema already documents the parameter as a case-insensitive region tag, so baseline is 3. The description adds value beyond the schema by supplying concrete example values and identifying the authoritative source tool for tags, which helps the agent construct a valid call.

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 verb+resource ('Open-lift totals for a whole region') and explicitly distinguishes itself from resort-level siblings by saying it returns 'each resort's count' for the whole region. It also anchors the 'region' concept to ski_list_regions, so an agent can tell it apart from ski_get_resort_status without opening a 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 states where the region value comes from ('a tag from ski_list_regions, e.g. "Utah", "Dolomiti"'), which is genuine routing guidance. It gives no explicit when-not-to-use or comparison against ski_get_resort_status / ski_open_now, so context is clear but alternatives are not named.

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