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

Annotations already carry readOnly/idempotent/non-destructive/closed-world, and 'Read-only' merely restates them. However, the description adds real context beyond annotations: images and scripts are stripped, the payload is widget-only metadata, and the design must be owned by the caller.

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?

One dense sentence, no filler, with the producing context front-loaded. The 'so the card can outline a section' clause is slightly inside-baseball for an agent but earns its place by explaining the return shape's purpose.

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?

An output schema exists, so return values needn't be spelled out, and the ownership plus stripped-content facts are covered. Still missing is any disambiguation from iter0_get_design, which returns presumably related data and is the most likely wrong pick for this task.

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 0% for the single designId parameter, so the description must compensate. It adds the meaningful constraint that designId must refer to an owned design, but gives no format, source, or validation hints.

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 states concretely what is returned: a light copy of an owned design's page in widget-only metadata. This differentiates it in substance from iter0_get_design and iter0_read_canvas_page, though it never names those siblings, and the 'measure/layout' framing in the name does not obviously map to 'return a page copy'.

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?

'Used by the iter0 card' and 'when the person points at the preview' imply a trigger context, but there is no explicit when-to-use versus iter0_get_design or iter0_read_canvas_page, and no when-not guidance. Usage is inferable rather than stated.

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