zoom

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

With no annotations, the description carries full burden. It explicitly states 'This tool is read-only for inspecting detail' and warns that coordinates in subsequent clicks refer to the full-screen screenshot. It does not describe all edge cases but covers the key behavioral trait.

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 short (4 sentences), every sentence adds value, and the key information is front-loaded. It is well-structured and easy to parse.

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?

The description covers purpose, usage guidance, and behavioral transparency. Given no output schema, it does not need to detail return values. It is complete for the tool's complexity, though could mention the result type briefly.

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 coverage is 100% for both parameters. The description adds minimal additional meaning beyond the schema, such as confirming the coordinate space for 'region'. This meets the baseline but does not significantly enhance understanding.

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's purpose: 'Take a higher-resolution screenshot of a specific region of the last full-screen screenshot.' This distinguishes it from the sibling tool 'screenshot' which captures a full screen.

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 advises to 'Use this liberally to inspect small text, button labels, or fine UI details that are hard to read.' It also provides a critical warning about coordinate systems. However, it does not explicitly mention when not to use it or alternatives.

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