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

Annotations already declare non-readOnly, non-destructive, non-idempotent, closed-world, so the safety profile is covered. The description adds that the created UI is 'sized' and 'linked' beside the screen, but it doesn't explain what linking does to the document, whether existing boards are affected, or whether the call is repeatable — modest added value.

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?

A single front-loaded sentence with a clear use-when clause and zero filler. It is compact and readable, though the clustered enumeration of kinds makes it slightly dense.

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 6-param mutation tool with a nested trigger object and no output schema, the description covers purpose and placement but says nothing about the return value (e.g., the created board id) or how the trigger is resolved when both shape_ids and label are present. Adequate but with clear gaps.

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 coverage is 83%, so the schema itself documents most parameters including the kind enum and trigger object. The description reinforces the kind list and the 'beside its screen' placement but adds no syntax or format detail beyond the schema — baseline 3 applies.

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 (adds) and a concrete resource set (dropdown, side, sheet, dialog, state board) plus the placement constraint 'beside its screen'. It is distinguishable from siblings like add_artboard because the enumerated kinds are unique to this tool, though no sibling is named for contrast.

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?

'Use when a control opens hidden UI' gives an explicit trigger condition that tells the agent the scenario for invoking this tool. It stops short of naming alternatives or when-not-to-use cases, so it lands just below the top band.

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