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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: it is all-or-nothing ('Errors if any slug is invalid'), meaning a single bad slug fails the whole batch, and it warns about array coercion for single values.

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?

Front-loaded with purpose and return fields, then routing, then the failure mode and array rule — a sensible order with no filler. The 'REQUIRED arguments: locationSlugs' line largely repeats the schema's required array, so it is mildly redundant.

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 tool with annotations covering safety and no output schema, the description covers return fields, error semantics, and input coercion. Minor gaps remain, such as any limit on how many slugs can be passed in one call.

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% with an example, so the parameter is documented structurally. The description still adds meaning: it clarifies the parameter accepts 'one or more' slugs and that a single value must still be wrapped in an array — a real failure mode not stated in the schema.

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 (look up) and resource (location slugs by identifier) and enumerates exactly what is returned: name, type (country / metro-DMA / state), parent country, currency, coordinates. It also implicitly separates itself from the name-based search path by pointing to search-locations.

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?

Explicitly says 'Use search-locations first if you only have a name,' giving a clear routing condition to the most confusable sibling. However, it does not distinguish itself from get-location-stats, another location sibling an agent could plausibly pick for detail-style queries.

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