screenshot

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

With no annotations provided, the description carries the full burden. It discloses that the screenshot is half-resolution JPEG, explains why a raw full-res PNG would overflow the MCP tool-result token cap, and quantifies the payload reduction (4-8x). It even notes a lasting fix is tracked. This is outstanding transparency about behavior and limitations.

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 moderately sized and front-loaded: the first sentence states the action and return value, the second gives a quick use case, and the third explains the compression rationale. Each sentence earns its place, though the parenthetical reference to 'feature #8' is slightly internal. Structure is clear and logical.

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 a single required parameter, the description covers the core behavior, output format, and important performance constraints. Since an output schema exists, it need not detail the JSON structure. The only shortcoming is the missing parameter guidance, but that is already accounted for in the parameter semantics dimension.

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 only parameter is 'device' with a string type in the schema and no schema description. The description's coverage is 0%, and the description itself never mentions the 'device' parameter, its meaning, or accepted values. Since the description must compensate for the schema gap, this is a significant omission, leaving the agent without guidance on what to pass.

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 starts with 'Take a screenshot of the device screen' – a specific verb and resource – and immediately states the return type (base64-encoded JPEG). It clearly distinguishes this plain screenshot tool from siblings like screenshot_annotated and screenshot_cropped via the phrase 'shared compressed screenshot path'.

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?

It explicitly says 'Use this to SEE what's on screen before deciding what to tap', giving a direct use case. It also explains the trade-off with token limits, which helps in selecting this tool over potentially richer alternatives. However, it does not explicitly mention when not to use it or name alternative tools for comparison, leaving a slight gap.

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