playbar

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

Adds substantial state-change context beyond annotations: frame changes persist across calls and for the user, 'range' alters flipbook coverage and any ROP following $FSTART/$FEND, and 'play' requires a GUI. Annotations (readOnlyHint=false, idempotentHint=true, destructiveHint=false) already flag mutation and idempotency; the description complements rather than contradicts, though it does not say what 'play' does to an in-progress cook or how long it blocks.

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?

Purpose and usage constraints are front-loaded in two short blocks, with the mode enumeration after — the right ordering for an agent deciding whether to call. The mode list duplicates the schema's enum, which is some redundancy, but each line adds a behavior not stated in the schema (e.g. playback range sits inside the scene range).

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?

Covers prerequisites (GUI for playback), blast radius (persistence for the user, flipbook and $FSTART/$FEND ROP ranges), and the alternative tools to prefer for non-persistent reads. With an output schema present, no return-value explanation is needed, and nothing an agent needs to call this correctly is missing.

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 the baseline is 3; the description earns one better by mapping each parameter to the modes that consume it (frame for 'frame', start/end for 'range' and 'playback', action for 'play') and listing the action values, giving a coherent per-mode picture. Much of this restates the schema's own parameter descriptions, so it is not a large increment.

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+resource ('Read or set the time of the session') and immediately enumerates the five modes, so the agent knows exactly what surface the tool covers. It is clearly distinct from the read-only inspectors named as siblings.

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?

Explicit when-to-use ('before you read geometry that changes over time: a SOP cooks at the current frame') and explicit when-not-to-use (geometry_inspect, node_inspect, stage_inspect take `frames` and restore the playbar). The rationale for the distinction — a frame set here persists for the person and for later calls — makes the tradeoff legible.

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