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

Annotations already cover readOnlyHint and openWorldHint, so the bar is lower. The description still adds real behavioral value: it discloses that rows contain company names and qualifiers, and warns to check total/has_more for incomplete coverage after upstream fallback, which the annotations do not convey.

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 tight sentences, front-loaded with the core fetch action and scope, then edge behavior, then sibling routing. Each sentence earns its place; minor filler in 'other company-credit' phrasing but nothing 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?

With an output schema present, return values need not be explained, yet the description still flags total/has_more for pagination. Combined with annotations and the routing guidance, an agent has everything needed to call it correctly.

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 the baseline is 3. The description goes beyond the schema by clarifying that exactly one of id or url is expected ('exactly one title id (tt...) or title URL') even though required count is zero, disambiguating the mutual-exclusivity the schema leaves implicit.

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 (IMDb production-company, distributor, and other company-credit sections), scoped to exactly one title. It names the siblings it is NOT (imdb_title_credits, imdb_title), so an agent can distinguish it without opening schemas.

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?

Explicitly routes the agent: use imdb_title_credits for cast/crew and imdb_title for title metadata, and the scope is limited to one title id or URL. This is clear selection guidance, though it stops short of stating when company credits should be retrieved or any exclusions.

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