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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety and external-data profile is covered by structured data. The description adds nothing beyond that: no note on recommendation basis, result ordering, or why the limit is clamped to 25.

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 four-word fragment with zero filler, and it is front-loaded. It is efficiently sized for what it attempts, though brevity here reflects under-specification rather than disciplined editing.

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?

The rich schema, output schema, and annotations carry most of the load, so the definition is minimally callable. Still, nothing explains that the id must come from a prior JustWatch lookup or how this differs from sibling recommendation surfaces, leaving a real gap for agent routing.

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 id format (tm[0-9]+/ts[0-9]+), the default limit of 10 with a 25 clamp, and the country/language defaults are all documented in the schema. The description contributes no additional parameter meaning, 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?

The phrase 'JustWatch similar titles' names the resource (similar titles) and the domain (JustWatch), which distinguishes it from siblings like justwatch_title or justwatch_title_offers. However, it is a noun fragment with no verb, so the action (fetch/list recommendations for a given title) is only implied rather than stated.

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 guidance on when to use this tool, what prerequisite it has (an existing JustWatch title id from search or title lookup), or how it relates to alternatives such as justwatch_search or justwatch_title_analysis. The agent must infer the whole workflow.

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