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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds genuinely non-obvious behavioral caveats: 'Configured calendars are not proof of available data' and 'International coverage is incomplete,' which warn about data-coverage semantics an agent cannot infer from annotations or schema. It stops short of describing pagination or output shape, but the output schema exists.

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?

Four sentences, all earning their place, with the primary purpose front-loaded before the routing guidance and caveats. Slightly dense but no filler or repetition.

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?

Combined with an output schema (which carries return-value detail) and annotations (which carry the safety profile), the description supplies everything else an agent needs: purpose, selection rule, named alternative, and data-coverage caveats. Nothing material is missing for a zero-parameter catalog tool.

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?

The tool takes zero parameters and the input schema is an empty object, so the baseline is 4. There is nothing parameter-related for the description to compensate for, and it correctly implies a no-argument discovery 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 (Discover) and resource (available public-holiday calendars and exact region ids, published years, source kind, freshness), and explicitly distinguishes itself from the sibling get_public_holidays. An agent can immediately tell this is a catalog-discovery tool rather than a data-fetch tool.

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 the exact condition for use ('when country/region/year coverage is unknown') and routes the agent to the alternative ('otherwise call get_public_holidays directly'). This is explicit when/when-not plus the named alternative, the top of the scale.

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