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

Annotations flag this as destructive (destructiveHint=true, readOnlyHint=false), so the agent knows it mutates state, but the description adds nothing about irreversibility, whether the original can be restored via restore_original_image, or what 'the selected image' means when options.elementId/imageFile also exist. For a destructive mutation the bar is higher than a single generic sentence.

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 short sentence with no waste, but 'using the existing image tool' contributes no information and the brevity comes at the cost of substance rather than being efficient.

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?

A destructive, session-scoped mutation with a deeply nested options schema and no output schema needs to say what happens to the image, whether it is reversible, and what the caller gets back. None of that is present.

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% and the nested options/placement objects are documented in the schema, so baseline 3 applies. The description adds no meaning: it doesn't clarify how the 'selected image' resolves against elementId, elementIds, or imageFile, which is the one thing the schema leaves ambiguous.

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 ('invert ... image's colours'), so the operation itself is unambiguous. However, it doesn't distinguish itself from adjacent image-editing siblings such as flip_image, remove_background, or crop_image, and the trailing 'using the existing image tool' is ambiguous filler.

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 indication of when to use this rather than flip_image, remove_background, or replace_image, and no prerequisites (e.g., that an image element must already be selected in the current session). The agent is left to infer everything about selection conditions.

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