Preview Frame

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

Annotations already declare readOnlyHint/idempotentHint/non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context the annotations do not: image output costs tokens by size, the tiling layout of a multi-time result, and the recommendation to batch times in a single call. It does not mention rate limits or output format, but the added cost/layout disclosure is substantive.

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?

The purpose and the cost/batching advice are front-loaded and tight. The final sentence about 'scene / scenes' in an edit does not earn its place — it references concepts absent from the schema and could mislead an agent into looking for non-existent parameters.

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 read-only, no-output-schema preview tool, the description covers purpose, output shape (one tiled image), size defaults, and cost trade-offs, which is most of what an agent needs. Remaining gaps are minor (exact image format, max frame count is only in the schema) but the confusing scene/scenes sentence slightly undermines it.

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 67% (comp_id is undocumented anywhere), and the description reinforces the size/time semantics ('keep the default size', tiling order for multiple times). That is helpful but largely restates the schema's own size and time descriptions, and the trailing 'scene / scenes name the precomp each frame shows' refers to parameters that do not exist in the schema, adding confusion rather than clarity.

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?

The description states a specific verb and resource ('Render comp frames and return them as one image') plus the composition mechanism ('several times are tiled left to right, top to bottom'). This clearly separates it from render_start/render_status, though no sibling is named explicitly, so it stops short of a 5.

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?

It gives concrete call-pattern advice ('keep the default size', 'pass several times in one call rather than calling once per time'), which is real guidance on how to invoke it efficiently. However it never states when to prefer this over render_start or the other render tools, and offers no exclusions, so usage is only implied.

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