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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds that results include core metadata and available offers, but discloses nothing about rate limits, auth, or failure modes for an unknown/invalid ID. Some added value over the annotations, but not rich.

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?

Two tight sentences, front-loaded with the core action and then the selection condition. No filler, though the return-contents clause is somewhat redundant given an output schema exists.

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 an ID-keyed lookup with an output schema and read-only/open-world annotations, the description covers what is needed to invoke it correctly. The main residual gap is not pointing to the sibling used to obtain the ID in the first place.

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%, so the id/country/language semantics (including the tm/ts ID pattern and ISO code defaults) are fully documented in the schema. The description only echoes 'raw GraphQL ID' and mentions no parameters, so it adds little beyond the structured fields. 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 (fetch), resource (JustWatch movie or show), and the key qualifier 'by its raw public GraphQL ID', which implicitly separates it from ID-less siblings like justwatch_search and URL/slug-based justwatch_title. It stops short of naming the sibling it differs from, so an agent must infer the distinction.

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?

'Use this when you already have the JustWatch title ID' gives a clear precondition for selection. It does not name the alternative to use when the ID is unknown (e.g. justwatch_search), which matters given the large JustWatch sibling set, but the usage context is otherwise explicit.

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