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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds useful context beyond that: 'public' IMDb data (no auth implied) and the mutual-exclusivity constraint 'pass exactly one' — behavior the schema does not enforce via oneOf. It does not describe return shape, but an output schema exists.

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 with zero waste: purpose first, then input constraint, then sibling routing. Each sentence earns its place.

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?

For a two-param read tool with full schema coverage, an output schema, and annotation coverage of safety, the description supplies the missing pieces (exactly-one constraint, id format, sibling disambiguation). Nothing an agent needs to call it correctly is 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 coverage is 100%, so the baseline is 3, but the description adds a genuine constraint absent from the schema: exactly one of id or url must be supplied (the schema shows both as optional and permits neither/both). It also gives the expected id format (nm...) and URL shape, exceeding the schema's terse descriptions.

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), resource (IMDb filmography sections), and scope (for a person), which is distinct from imdb_name (metadata) and imdb_title_credits (title cast/crew). An agent can differentiate it from siblings 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: names imdb_name for person metadata and imdb_title_credits for a title's cast and crew, implying when this tool is the right choice (filmography for a person). Nothing is left to inference.

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