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

Annotations cover the safety profile (readOnlyHint, openWorldHint), so the bar is lower, and the description still adds real value: the limit default and 20 cap, the constraint that it 'cannot bypass IMDb's initial page slice', the hint to check total and has_more, and the error behavior for sign-in walls. These are operational traits not derivable from the annotations.

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?

Front-loaded with the resource and locator rule, then the limit constraint, then routing advice. Dense but every clause carries information; the semicolon-packed opening is slightly heavy but not wasteful.

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 spelled out, yet the description still flags total/has_more for pagination and the sign-in-wall error. Combined with the limit cap and sibling routing, an agent has what it needs; only finer-grained pagination mechanics are left implicit.

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%, setting a baseline of 3, but the description adds meaning beyond the schema: that id and url are mutually exclusive locators ('pass exactly one locator') and the limit default/cap behavior. That mutual-exclusivity rule is not encoded in the schema and is genuinely useful.

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 ('Fetch') and resource ('public IMDb user reviews, ratings, spoiler markers, and helpful-vote counts') and scopes it to a title id (tt...) or URL. It also explicitly names the sibling it is not (imdb_title for metadata), so an agent can separate it from imdb_title_ratings and imdb_title without opening a schema.

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 a clear alternative pointer ('Use imdb_title for title metadata') and states the locator rule ('pass exactly one locator'), which tells the agent how to call it. It lacks explicit when-not-to-use conditions beyond the metadata case, so it falls just short of 5.

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