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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, covering safety. The description adds the detail that the destination's host calls this list_facets, which is peripheral. It doesn't disclose return format or error behavior, but with annotations present, the bar is lower; still, more context could be added.

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 a single sentence that is efficient and front-loads the verb and resource. The added parenthetical about the host's naming is slightly extra but not wasteful. It earns points for being concise and well-structured.

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?

Given the tool's simplicity (2 params, 100% schema coverage, output schema present, annotations provided), the description is mostly sufficient. It lacks explicit mention of what the output structure looks like, but output schema exists to cover that. It could mention that it returns filter values for all three families by default, but the schema's default covers that. Overall adequate with minor gaps.

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 has 100% coverage for both parameters: 'kind' is described as 'Return only this facet family; omit for all three,' and 'destination' is described as 'Destination name or slug; call search_destinations to discover one.' The description adds no additional parameter information beyond what schema already provides, so baseline 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?

States a specific verb ('list') and resource ('a named destination's valid area, category and tag filter values'). It distinguishes from siblings by focusing on facets, but could explicitly differentiate from facet_vocabulary. The mention of the host's own name 'list_facets' adds clarity but the purpose is clear enough.

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?

Implies usage when you need filter values for a destination, and the 'kind' parameter hints at selectivity. However, it doesn't explicitly say when to use this vs facet_vocabulary or search_destinations, though the schema provides some guidance via parameter descriptions. Lacks explicit exclusions or alternatives.

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