Which thumbnails are rising or falling

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

With no annotations, the description carries the transparency burden. It discloses the key behavioral trait: comparison against the item's own earlier half, and warns that missing history means nothing to compare. It does not describe the exact output structure or behavior for empty history, but it provides sufficient directional context for the tool's behavior.

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?

Three sentences with no filler: the first explains what the tool does, the second gives when to use it, and the third states a necessary caveat. Information is front-loaded and every sentence earns its place.

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 3-parameter tool with no annotations and no output schema, the description covers purpose, use case, and a critical prerequisite. It could be more complete by describing the return shape or the exact behavior for recently added games, but the provided text is sufficient for an agent to select and invoke the tool correctly in most situations.

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%, so all three parameters are already fully documented in the schema. The description adds only marginal context by referencing 'window' and 'stored history' but does not elaborate on parameter semantics beyond what the schema provides.

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 clearly states the tool's function: determining per-thumbnail QPTR direction (climbing/sliding/flat) over a window, compared against each thumbnail's own earlier half. It distinguishes itself from sibling tools by emphasizing self-comparison rather than comparing against other thumbnails, which is a strong purpose differentiation.

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?

The description gives an explicit use case ('decide what to drop when a game's overall numbers are fine but something in the set is dragging') and a clear prerequisite/caveat ('Needs stored history'). It does not name alternative sibling tools, but the comparison methodology and use case make the intended context clear.

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