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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds the shape of the payload (fields returned), which is mildly useful context, but says nothing about auth, rate limits, error behavior, or missing-ID handling. Adequate but not rich against an already-covered annotation set.

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 sentences, front-loaded with the action and resource, then the payload and the ID provenance. No filler, no restated name.

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, the description needn't enumerate return fields, yet it does so harmlessly. The only real gap is behavioral context (errors, invalid IDs, rate limits), minor for a simple read-only detail endpoint.

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% and the schema already documents the id field with an example, so baseline is 3. The description goes beyond that by specifying the ID's provenance ('returned by TMDB search'), which clarifies where a valid value comes from—useful semantics the schema does not carry.

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 ('Fetch a TMDB movie by movie ID') and implicitly scopes it against siblings like tmdb_tv and tmdb_search. An agent can immediately tell this is the by-ID detail lookup, not a search or list tool.

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 a movie ID returned by TMDB search,' which tells the agent the prerequisite step and the sibling that produces valid input. It stops short of naming when-not-to-use or listing alternatives such as tmdb_tv, so it is clear context without full exclusion guidance.

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