Describe image (UI / web page / layout)

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

Annotations already mark this as readOnly and non-destructive. The description adds valuable behavioral context by enumerating the output structure (text, interactions, accessibility) and accepted input formats (URL, local path, base64), going beyond the annotation's bare safety hints.

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?

The description is three concise sentences that front-load the purpose and output, then cover use cases and input formats. Every sentence contributes information, with no redundancy or filler.

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?

Given the readOnly annotation, an output schema, and the tool's complexity, the description covers all necessary aspects: input variants, optimization targets, and output richness. The presence of an output schema makes a detailed return-value explanation unnecessary, so no gaps remain.

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 100% with all three parameters clearly described. The description mentions the accepted input formats, but this duplicates the 'image' parameter's schema description without adding new semantic detail. It achieves the baseline for high schema coverage.

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 clearly states the tool 'Analyses an image' and specifies the rich output categories (layout hierarchy, UI components, text, interactions, design notes, accessibility). This is a specific verb+resource pair that fully conveys what the tool does and distinguishes it from any conceivable alternative.

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?

The description provides clear context by noting it is 'optimised for UI mockups, HTML/CSS screenshots, Figma exports, dashboards, and web/app interfaces,' which implies appropriate use cases. Since there are no sibling tools, explicit alternatives are unnecessary, but exclusionary guidance is absent.

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