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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuine behavioral detail beyond that: the backend is the public JustWatch GraphQL endpoint, limit is clamped to 50, and cursor is an opaque next_cursor token for pagination.

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?

Compact and front-loaded: purpose first, then parameter notes, then the sibling pointer. Some sentences duplicate schema content, which is mildly redundant but keeps the definition readable.

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?

An output schema exists, so return values need not be explained. The description covers the source, pagination, clamping, and country default, leaving only minor gaps like the language parameter, all of which the schema already handles.

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 the schema already documents all five parameters. The description largely restates type values, limit default/clamp, cursor, and country — it adds no syntax or semantics beyond the schema and omits the language parameter entirely. 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 and resource (returns popular movies and shows) and even names the data source. It routes to justwatch_new, but doesn't distinguish itself from other JustWatch 'list' siblings such as justwatch_discover or justwatch_monetization_titles, so full sibling differentiation is missing.

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 names an alternative and the condition that selects it ('Use justwatch_new to get new JustWatch titles'), giving a clear when-not. However there is no positive when-to-use context (e.g. 'use this for trending/popular browsing vs discover').

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