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

No annotations are supplied, so the description carries the full behavioral burden and delivers very little. It does not say whether unspecified fields are left untouched or cleared, whether the change is undoable, whether the editor must already contain the asset, or what a failure looks like. 'In the open editor' is the one useful disclosure about required 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?

A single front-loaded sentence with no filler or redundancy. It is efficiently structured, though for an 8-parameter mutation tool the terseness borders on under-specification rather than serving brevity.

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 an 8-parameter write tool with no annotations, no output schema, and only 50% schema description coverage, the description leaves most of what an agent needs unaddressed: update semantics, partial-vs-full replacement, and half the parameter meanings. Only the basic purpose and the editor-state hint are covered.

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 exactly 50%: x, y, width, and height are documented in the schema, but src, rotation, assetId, and screenshotId are not. The description adds no parameter meaning at all, so the under-documented half of the parameters is unexplained in both places. With low coverage the description is expected to compensate and does not.

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 (Update) and resource (an image layer on a screenshot), which is enough to distinguish it from update_div, update_text, and update_phone. It does not, however, explain how it relates to the near-sibling add_asset/remove_asset or why the name says 'asset' while the description says 'image layer'.

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?

No when-to-use guidance, no prerequisites, and no mention of alternatives such as add_asset (for new layers) or update_screenshot (for whole-screenshot changes). The only contextual clue is the phrase 'in the open editor', which hints at a required editor state but does not spell it out.

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