Play an animation

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

With no annotations, the description carries the full burden. It usefully discloses the default looping behavior and the format limitation, but says nothing about whether a playing animation replaces or overlays existing screen content, what happens on subsequent calls, whether playback is blocking, or what is returned.

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?

Four short sentences, each earning its place: valid values and their source, size semantics, default looping, and the unsupported-custom constraint. The most decision-relevant information (stock only, names from bar_stock) is front-loaded.

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 playback tool with no annotations and no output schema, the description covers the input name contract well but leaves the display/positioning and caption parameters and the effect on current screen state unexplained. Adequate to call it, not enough to predict its behavior.

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 only 38% across 8 parameters, so the description must compensate. It does add real meaning for the required `name` (stock-only, size encoded in the filename, 72x16 fills the front screen), but x/y positioning, caption, and caption_color remain undocumented anywhere, and `loop`/`display` are already covered by 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?

"Play one of the Bar's stock animations" gives a specific verb and resource, and it routes the agent to bar_stock for the name list and away from bar_image/bar_text. The constraint that custom animations are unsupported further sharpens the boundary so the sibling set is easy to disambiguate.

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 names the prerequisite source of valid values (bar_stock) and states an explicit exclusion (custom animations not supported, closed format). It does not say when to prefer an animation over bar_image or bar_text on the same display, so the alternative selection is only implied.

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