screenshot

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

With no annotations, the description carries full behavioral burden. It does not disclose prerequisites (e.g., screen recording permission), side effects, or the format of results (since there is no output schema). The description implies a read-only capture but never states what happens after capture (returns image? saves file?), which is a significant gap for a tool with no annotations.

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 extremely concise—three short sentences, with the core action front-loaded and no superfluous content. It encodes the purpose and usage decision in minimal words, earning its place.

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 2 optional parameters (one nested), no output schema, and no annotations, the description is incomplete. It lacks parameter explanations, return value details, and any prerequisites. While it gives clear usage guidance, the missing behavioral and parameter context prevents an agent from invoking it correctly in many scenarios.

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 description coverage is 0%, and the description does not explain any parameters. The parameters app_ref and display_id are undocumented, leaving the agent to guess their meaning. The description only says 'full-display screenshot,' which does not clarify how display_id or app_ref influence the capture, so it fails to add value beyond the schema's bare property names.

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 states a clear verb-resource pair: 'Capture a full-display screenshot.' It also differentiates the tool from its sibling get_app_state by explicitly stating when it is appropriate ('when accessibility cannot express the target and pixel coordinates are needed'), which separates it from other UI tools like clicks and key presses.

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 explicit usage guidance: 'Prefer get_app_state' and 'Use this only when accessibility cannot express the target and pixel coordinates are needed.' This tells the agent when to use this tool versus the alternative, leaving no ambiguity.

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