Screenshot diagram

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

Annotations only cover the safety profile (readOnly, not open-world), so the description carries the rest and does so well: it discloses the prerequisite ('Needs the preview tab to be open') and that a page selector renders a non-visible page 'without changing what the user sees'. The one incompletely covered trait is whether the call has any side effect on the preview state.

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 front-loaded sentences ordered by importance: action, when to call, then page-selection semantics and prerequisite. 'so you can see your own result' is mildly redundant but justifies the tool's existence rather than padding.

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 no-output-schema tool it covers the essentials: what is returned (a PNG image), the prerequisite tab state, and the page targeting behavior. Nothing critical is missing, though a note on what happens if the preview tab is not open would fully close the loop.

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 page_id/page_name/page_index and their precedence are already fully documented in the schema. The description only adds the behavioral distinction between supplying vs omitting a selector, not new syntax or format detail, which is the expected 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?

States a specific verb and resource ('Render the diagram ... return it as a PNG image') plus the intent ('so you can see your own result'). It does not distinguish itself from the sibling export_diagram, which likely overlaps in producing an image, so an agent must still infer which one to use.

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?

Clearly says when to call it ('once after drawing or heavily editing a complex diagram, then fix overlaps and edges that cross shapes') and implies not to call it repeatedly. It never names the alternative (export_diagram) or states when not to use it, so the routing guidance is contextual rather than explicit.

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