playtest_frames

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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, and the description's closing 'Read-only' merely restates that. It does add real context beyond annotations: the tool consumes pre-existing screenshots from a finished run and returns a single sheet ordered left-to-right, top-to-bottom. However, it omits what happens when no screenshots exist or when maxFrames truncates the selection.

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 core function in the first sentence, then use case, then parameter semantics. Length is justified by eight undocumented parameters, though the parenthetical probe list ('is the weapon in the hand, does the blow land...') is stylistically loose and adds bulk.

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 an 8-parameter tool with zero schema descriptions and no output schema, the definition supplies most of what an agent needs: units, ranges hinted externally, layout order, and preparation steps. Gaps remain around maxFrames' truncation behavior and failure modes (missing or too few screenshots).

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?

With 0% schema coverage the description carries the full load and mostly succeeds: fromSeconds/toSeconds are 'play seconds, the clock of the screenshots', every is 'each n-th', crop is [x0,y0,x1,y1] as screen fractions, columns and width are sheet layout in pixels. It also cites external limits (screenshotsAt up to 120, screenshotWidth up to 3840). maxFrames and runId are left undocumented, keeping it short of a 5.

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 concrete verb and resource: 'Put the screenshots of a finished playtest side by side in one picture, each cut to the same part of the screen and labelled with its play second.' The framing 'the way to look at motion' makes the tool's role unmistakable and distinct from any sibling, none of which produces composite frame sheets.

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 clear triggering condition (verifying motion, e.g. does the blow land when the number comes up) and concrete preparatory guidance: shoot a quarter/half second apart via playtest_start's screenshotsAt, zoom with scene_set_camera or rely on crop. It also advises iterating with two sheets (a wide one to find the moment, a close two-second one). No explicit 'when not to use' or named alternative tool for this function.

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