Capture Screenshot

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

Annotations already declare idempotentHint=true and destructiveHint=false. The description adds the return behavior: inline image when true, and a JSON object with { success, filename, bytes } when false, plus the note that hosts render the image. It also discloses password optionality. This goes beyond the annotations without contradicting them, though it doesn't mention any side effects (none expected given idempotence).

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 four sentences, each with a purpose: core action, host rendering context, parameter usage guidance, and password note. It is front-loaded with the primary behavior and then provides conditional details. Slightly longer than necessary but every sentence adds value, so it earns a 4.

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 4 parameters, no output schema, and annotations present, the description explains the return format in both modes, when to use the boolean, and password handling. It does not cover error cases or what happens if the device is unspecified, but those are covered by schema and the focused-device concept. The description is sufficient for correct invocation.

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%, so the baseline is 3. The description adds meaningful context for `returnImageBase64` (when to set false) and clarifies password behavior ('optional when Dev Studio has remembered it'), which reinforces the schema. For `device` and `waitAfterTriggerMs`, the schema already explains them, so the description adds no extra value there, but the added emphasis on the boolean is valuable.

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 action ('Capture a screenshot of the current device screen') and the resource (the device screen). It also specifies the return format ('inline as an MCP image content block (JPEG, base64)'), which distinguishes it from other tools. No sibling performs the same function, so differentiation is inherent, but the description is precise and 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 gives explicit guidance on when to use the `returnImageBase64` parameter: 'for any human-facing capture let returnImageBase64 default to true (or omit it)' and 'Set returnImageBase64: false ONLY for batch / metadata-only flows'. It also notes the password is optional when remembered, covering usage prerequisites. This is clear, actionable usage direction.

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