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

Annotations already cover safety (readOnly, idempotent, non-destructive), yet the description adds a non-obvious rendering constraint: a Pro-piece film on a non-Pro plan renders at half size, and a full-size frame of it is a poster requiring export_poster. It also discloses that a shot is only viewable once its elements have arrived. Neither fact is derivable from the schema or 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 its resolution, then the use case, then selectors, then the caveat. The final sentence is dense and slightly tangled (poster/export_poster detour), but every sentence carries information.

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?

Five parameters are fully described in-schema, annotations cover the safety profile, and the description adds defaults and a plan-based fidelity caveat. It never states outright that the tool returns an image artifact (rather than a URL or an id), which is the one detail an agent must still infer.

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 baseline is 3, but the description adds the precedence/default behavior between 'at' and 'shot' — first shot when neither is given — which the schema does not state. The half-size caveat also gives the 'format' parameter context it lacks in the schema.

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 ('ONE frame of the film at full size, 1920×1080 in 16:9') and explicitly contrasts it with a contact sheet, which is named as the too-small alternative. An agent can immediately tell this is the zoom-in inspection tool rather than a preview or listing 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?

Gives a concrete trigger ('to read small text or check a detail a contact sheet is too small for') and states the default when neither selector is supplied ('without either, the first shot'). It does not name the sibling contact-sheet tool explicitly, so the routing is implied rather than spelled out.

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