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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds one genuinely useful behavioral detail - that it returns 'technical names' rather than display labels - but says nothing about auth, rate limits, or how the list is scoped/ordered.

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 with zero filler - the resource and scope are stated immediately and nothing redundant is included for a one-parameter lookup tool.

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?

Complexity is low, the parameter is fully documented in the schema, safety is covered by annotations, and an output schema exists so return values need not be explained. The only real gap is the absence of any hint about how the returned certifications are meant to be used.

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 description coverage is 100%, and the schema already documents the single optional country parameter with an ISO example and default US. The description's 'for a country' merely restates the parameter's role without adding format or behavior beyond the schema; baseline 3 applies.

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 (Returns), a specific resource (JustWatch age certification technical names) and scope (for a country), so an agent knows exactly what comes back. It does not explicitly differentiate itself from the many sibling justwatch_* lookups (genres, providers, monetization), though the resource is distinctive enough to be recognizable.

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?

There is no when-to-use guidance, no mention of what the returned certification names are used for (e.g., feeding a title search or filter), and no named alternative or exclusion. The agent must infer the role of this lookup purely from the name.

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