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

Annotations already declare readOnlyHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuine context beyond them: the exact payload contents and the fact that availability is a 'one-line summary' rather than full availability data. It does not mention behavior for unknown slugs or region-scoped deep links.

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: the payload comes first, the optional-parameter effect second. No filler or repetition of the schema.

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 carries the burden of describing return contents and does so field by field, including the conditional watch_summary. Only edge behavior (invalid slug, missing country) is unaddressed, which is minor for a read-only lookup.

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 both parameters (ISO alpha-2 country, slug-or-UUID) are already documented structurally. The description restates the country parameter's effect as a 'one-line availability summary' and adds no format detail for id_or_slug, so it meets but does not exceed the baseline.

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 — 'Full metadata for one documentary' — and enumerates the returned fields (synopsis, director, genres, topics, runtime, age rating, deep link), so an agent can tell this is the single-film detail lookup rather than a list. It never names search_documentaries or where_to_watch, so the separation from siblings is inferred 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?

The sentence about passing the country code to obtain an availability summary gives actionable conditional guidance for one parameter. There is no explicit statement of when to prefer where_to_watch for availability-only questions, nor any when-not guidance, leaving the overlap with the sibling to inference.

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