locate_element

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

Since annotations are absent, the description carries the behavioral disclosure burden. It reveals key behaviors: the use of a local Ollama vision model ('Claude never sees the image'), privacy preservation, and the coordinate system semantics for viewport_bounds. It does not describe failure handling, permissions, or output format, but the disclosed traits are meaningful and non-obvious.

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 sentences, each earning its place: core purpose, model/privacy, and coordinate behavior with a concrete example. The critical viewport_bounds guidance is front-loaded after the purpose, making the most actionable information easy to find. No filler words or redundancy.

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?

Considering the tool's complexity (nested viewport_bounds object, 5 params, no output schema, no annotations), the description covers the essential missing context: coordinate semantics and the crucial Chrome-specific computation. It omits edge cases like element-not-found behavior or return error structure, but for a coordinate-returning tool, the provided detail is sufficient for effective use.

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?

The schema already documents all 5 parameters with 100% coverage, so the baseline is 3. The description adds significant value by explaining exactly how to compute viewport_bounds for Chrome and why it changes the returned coordinates. This provides meaning beyond the schema's static field definitions.

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 opens with an explicit, specific verb+resource statement: 'Find a UI element in an app window and return its click coordinates.' This clearly differentiates the tool from siblings like analyze_screenshot (which analyzes an image) and capture_window (which captures a window). The returned artifact (click coordinates) is unambiguous.

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 concrete guidance for the Chrome-specific case, including a detailed formula for viewport_bounds and the consequence of omitting it (absolute vs. viewport-relative coordinates). It does not explicitly name alternative tools or state when not to use this tool, but it offers clear contextual usage instructions.

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