ui_diff_check

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

With no annotations, the description carries the burden of behavioral disclosure. It states the tool identifies visual differences and implementation discrepancies, but does not disclose whether it is non-mutating, what output format it returns, or any limitations/error behavior. The read-only nature is inferable from 'compare' and 'diff_check', but not fully explicit.

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 concise: four sentences, with the core purpose front-loaded in the first sentence. The subsequent sentences add value by specifying when to use, specialization, and exclusions without unnecessary repetition or fluff.

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 tool with three simple string parameters and no output schema, the description covers purpose, use cases, and exclusions effectively. It does not explain the return value or output format, but that is not critical for such a straightforward comparison tool; the description is sufficiently complete for an agent to select and invoke it correctly.

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%, with each parameter (expected_image_source, actual_image_source, prompt) described as local file path/remote URL or instructions. The description adds context by mapping 'expected/reference' to expected_image_source and 'actual implementation' to actual_image_source, but does not go beyond the schema in explaining parameter syntax or usage.

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 'Compare two UI screenshots to identify visual differences and implementation discrepancies', using a specific verb and resource. It also distinguishes this tool from siblings by focusing on UI quality assurance and design-to-implementation verification.

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 explicitly says 'Use this tool ONLY when the user wants to compare an expected/reference UI with an actual implementation' and lists clear exclusions: 'Do NOT use for: general image comparison, error diagnosis, or analyzing single UIs.' This provides effective when/when-not guidance, implicitly steering users to sibling tools like analyze_image or diagnose_error_screenshot.

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