set_page_wallpaper

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It reveals that the tool 'Writes the page outspace object', which indicates a mutation, but it does not explain whether this is an additive update to specific properties or an overwrite of the entire outspace object, what happens when color/transparency are null, or any side effects (e.g., whether existing wallpaper settings are replaced). The behavioral implications of a page outspace write are not fully disclosed.

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?

The description is three sentences, front-loaded with the main purpose, then providing a key distinction, parameter hints, and the underlying effect. Every sentence earns its place with no fluff or repetition.

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 simple 4-parameter tool with no output schema and no annotations, the description covers the primary purpose, the key distinction from the main alternative, and the underlying write operation. It lacks details on null handling and validation, but given the tool's apparent simplicity, it is reasonably complete. The main gap is the absent reportSessionId explanation, but this is likely a shared convention across tools.

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?

The schema already describes 75% of parameters (page, color, transparency), and the description adds little beyond reiterating 'color = hex, transparency = 0-100', which is largely redundant. The description does add context by linking the operation to 'the page outspace object', giving some meaning to the parameters' effect, but it does not compensate for the undocumented reportSessionId parameter. With schema coverage high, the baseline 3 is appropriate.

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 uses a specific verb ('Set') and resource ('page WALLPAPER') with a clear definition: 'the grey margin OUTSIDE the canvas'. It explicitly distinguishes itself from the sibling tool set_page_background by stating that set_page_background 'colours the canvas area', eliminating ambiguity.

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 clear guidance on when to use this tool versus the most similar alternative, set_page_background, by explaining the difference between wallpaper (outer margin) and background (canvas). It also notes that it 'Writes the page outspace object', implying the operation affects the page-level outspace. However, it does not discuss other potential alternatives or specifically state when NOT to use the tool.

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