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

With no annotations, the description carries the transparency burden. It reveals that the tool captures a window, returns a UI tree, and describes internal behavior ('Both modes walk the element tree internally to harvest nested text'). It implies a read-only snapshot, though it doesn't explicitly state side effects or permissions. This is adequate for a non-destructive capture tool.

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?

Three well-structured sentences: purpose, usage context, and parameter guidance. It is front-loaded, every sentence earns its place, and no filler is present.

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 read-only tool with no output schema, the description covers the essential aspects: what it captures, what it returns, and how to target a window. It is reasonably complete given the tool's simplicity, though it could nod to exceptional behaviors (e.g., accessibility restrictions or failure modes) for full completeness.

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 parameter descriptions, providing a baseline of 3. The description adds valuable guidance beyond the schema: 'Omit both window_title and process_name to inspect the currently focused foreground window,' which clarifies optionality and default behavior.

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 'Capture a window and return its UI element tree... plus a screenshot' using a specific verb and resource. It distinguishes itself from siblings by emphasizing the element tree and the 'without asking a specific question' use case.

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?

Explicitly says 'Use this to understand what is visible in an application without asking a specific question,' providing a clear when-to-use context. It does not explicitly mention alternative tools like 'capture' or 'query', but the guidance is still actionable, including the tip to omit parameters for the foreground window.

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