Sb3 Vm Pen Png

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions '(proxied)' without explaining what that entails, does not state whether the operation is read-only or has side effects, and does not describe any error or edge-case behavior. The return format is hinted at, but critical context is missing.

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 a single, compact sentence that front-loads the key output details (PNG base64 and pixel count). It is appropriately terse for a no-parameter tool. The parenthetical '(proxied)' is extra but does not bloat the text. It could benefit from a clearer structure, but it is concise and to the point.

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 tool is low-complexity (no params, output schema present), so the description need not explain return values. However, it omits usage context: no mention of when to call this versus related tools, no clarification of what 'proxied' means, and no indication of whether a project must be loaded. For a simple operation, this is marginally adequate but leaves gaps.

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 tool has zero parameters, so the input schema is trivially complete. Per the rubric, 0 parameters sets a baseline of 4. The description does not need to add parameter information, and it does not; it correctly focuses on the output.

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 the resource (pen raster) and the output (PNG base64 plus non-transparent pixel count). It is specific enough to distinguish from other VM tools like sb3_screenshot, though it lacks an explicit verb like 'retrieves' or 'returns', and does not name any sibling it is not. This is clear but not maximally differentiated.

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?

There is no guidance on when to use this tool versus alternatives. It does not mention any prerequisites, such as needing a loaded project, nor does it name any sibling tools for comparison. The description is purely informational and leaves usage inference entirely to the agent.

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