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

Beyond the annotations (readOnlyHint=false, idempotentHint=true, openWorldHint=true), the description discloses meaningful behavior: trailers play inline in apps with interactive results, the returned link opens the same list in a browser, and trailer language falls back to original-with-subtitles when no dub exists. It also describes per-title match/playability outcomes. It doesn't cover auth requirements or how long the created list persists.

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 sentences that are front-loaded with purpose, then behavior, then usage and return shape. Each sentence carries information and there is no filler, though the return-value sentence is dense and could be tightened.

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 no output schema, the description usefully compensates by describing what comes back for each title (matched title, year, TMDB id, playability status). Combined with annotations covering the safety profile, an agent has what it needs to invoke correctly; only auth and list-persistence details are absent.

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 items, title, and language are already fully documented in the schema, including the maxItems of 20 and enum values. The description's language note (dub when available, original-with-subtitles otherwise) largely echoes the language parameter's own schema description, adding little beyond it. 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 description opens with a specific verb and resource: 'Creates a trailer list on zinema.tv from movie and TV show titles.' That is unambiguous and clearly distinct from the read-oriented sibling get_list, though it never names that sibling explicitly. Purpose is clear without sibling differentiation.

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 when the user asks for movie or show recommendations, or wants to see trailers for specific titles' gives a clear triggering context. It stops short of stating when NOT to use it or naming get_list as the alternative for retrieving an existing list, so it lacks explicit routing guidance.

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