Preview frames

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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=false). The description adds genuinely useful behavior the annotations cannot convey: lossless PNGs, pixel-identical to the render, limited to one to two seconds of footage, and returned as images rather than paths.

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 core action and return format. Every clause earns its place, including the closing rationale for using the tool.

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 all three required parameters fully described in the schema and no output schema, the description fills the main remaining gap by explaining that images are returned directly. Minor omissions: no note on cost, latency, or behavior with out-of-range frame numbers.

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 description coverage is 100%, with all three parameters documented including frame-number examples, so the schema carries the load. The description adds nothing about parameters, though it does note the 1-2 second scope, which loosely constrains the frame count. Baseline 3 applies.

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 ("Draw some frames of a Kodecz video as lossless PNGs") and the return type ("return them as images"). It implies the relationship to `render` by saying the pixels match the render, but never names `render` or `check` to explicitly draw the boundary.

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?

"Use it to look at what you wrote instead of guessing" gives a concrete motivation and context for choosing this tool over blind edits. It stops short of stating when to prefer `render` or `check` instead.

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