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

Annotations already declare readOnlyHint and openWorldHint, so the safe/read-only and external-data profile is covered. The description adds that offers are returned only "when available," which is genuinely useful behavioral context, but says nothing about rate limits, pagination, or result ordering.

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?

Three short sentences, front-loaded with the action and scoping, followed by parameter formats and then alternative routing. No filler.

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?

With annotations covering safety and an output schema covering return shape, the description only needs to add selection and parameter nuance. It does that adequately, though it omits any hint about result volume or how offers appear in the payload.

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%, so limit/query/country/language are all documented in the schema. The description restates the ISO-code formats, which is redundant rather than additive, so the 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 and resource (search public JustWatch title cards) plus the notable side effect that offers are returned when available. It also names the sibling tools (justwatch_discover/popular/new) that serve the curated-list case, so an agent can distinguish it without opening schemas.

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 routes the curated-list use case to three named alternatives, which gives clear context for when to pick this tool. It does not spell out when-not conditions or required query semantics, but the alternative routing is unusually clean.

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