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

Annotations already declare readOnlyHint=true and openWorldHint=true, covering the safety profile. The description adds the country-focused scope, but says nothing about rate limits, per-country result shape, or how offers are ordered. With annotations doing the safety work, a 3 is appropriate.

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 sentences, both earn their place, with the core purpose front-loaded before the sibling routing. Slightly terse on return behavior but no wasted text.

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 described. Purpose, prerequisite id, and sibling relationships are all covered. Only minor gaps remain around behavioral detail (ordering, limits), which the annotations partly offset.

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 id, language, and countries are fully documented in the schema with formats and defaults. The description only echoes the country scoping and the raw-id requirement, adding no syntax or constraint detail beyond 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 (compare), resource (JustWatch availability for a known movie/show), and scope (across requested countries). It explicitly distinguishes itself from justwatch_title (main title record) and justwatch_search (id lookup), so an agent can route correctly.

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?

Gives explicit prerequisites ('known movie or show', raw title id from justwatch_search) and names the sibling to use instead for the main title record. The when/when-not conditions are spelled out rather than left to inference.

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