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

No annotations are provided, so the description carries the full burden of disclosing behavioral traits. It explains the conceptual purpose but fails to mention prerequisites (e.g., how the two snapshots/screenshots are supplied), side effects, or whether the operation is read-only. The tool's operational behavior remains opaque.

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 exactly two sentences, front-loaded with the core purpose, followed by targeted usage guidance. Every sentence earns its place with no redundant filler or repetition of schema details.

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 tool's complexity (30 parameters) and the existence of an output schema, the description adequately explains the high-level purpose and mode selection. However, it does not explain how to specify the inputs to be compared, nor does it address the `kind` const limitation. This leaves the agent uncertain about invocation mechanics, making the description adequate but incomplete.

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?

With 80% schema description coverage, the baseline is 3. The description adds the semantic-vs-pixel distinction, which provides some conceptual meaning, but it does not map these modes to specific parameters. Additionally, the schema's required `kind` field has const 'snapshot', which seems to conflict with the mention of 'screenshots', creating ambiguity that the description does not resolve.

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 uses a specific verb ('Compare') with a clear resource ('accessibility snapshots or screenshots') and an explicit outcome ('identify UI changes'). It also distinguishes two comparison modes (semantic vs pixel), differentiating this tool from sibling tools like snapshot and screenshot.

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 second sentence provides explicit context for when to use each comparison mode: 'Use snapshot comparisons for semantic tree changes and screenshot comparisons for pixel differences.' This is clear usage guidance, though it does not explicitly mention when not to use the tool or name alternative tools.

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