set_scale

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

With no annotations, the description carries the transparency burden. It discloses important behavioral details: coordinates are image px at render scale 2.0 with origin top-left and y-down, and the detected scale is never applied automatically. This goes beyond the schema by explaining the rendering coordinate space. It does not mention side effects like overwriting an existing scale, but the provided context is substantial.

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 core action, and every sentence adds distinct value: mode enumeration, automatic-detection caveat, and coordinate system. No redundant or vague phrasing.

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 tool with 5 parameters and a nested object, the description covers the essential context: modes, coordinate semantics, and the explicit-call requirement. A return value is not described, but an output schema exists. The description is sufficiently complete for an agent to invoke the tool correctly, though it does not explain how sheet is identified or what happens to prior scale settings.

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 80%, so the baseline is 3. The description adds meaning by explaining the coordinate system for calibrate points, giving an example label format, and clarifying that use_detected adopts the drawn scale note. It also clarifies the 'exactly as listed in the error' for label, which helps with validation. This exceeds baseline.

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 opens with a specific verb+resource: 'Set a sheet's scale'. It then enumerates the four mutually exclusive modes (label, upp, calibrate, use_detected), clearly distinguishing this tool from measurement or detection siblings. The added note that the detected scale is never applied automatically further clarifies its unique role.

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 explicitly states 'exactly ONE of' and explains each mode's purpose, giving clear context on when to use which option. It also warns that detected scale is never automatic, so the agent knows to call this tool explicitly to adopt it. However, it does not name alternatives or state when not to use this tool, so it stops short of full exclusionary guidance.

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