screenshot

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

Annotations already establish readOnlyHint=true, idempotentHint=true, and destructiveHint=false, which align. The description adds genuine value by disclosing the exact return shape { success, data: { dataUrl, width, height }, message? } and clarifying dataUrl is a base64 PNG. Missing details, like resolution behavior or error edge cases, keep it from a 5, but annotations lower the bar here.

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?

Two sentences, zero wasted words. First sentence states the action; second provides the return structure. Every phrase earns its place, and the structure is front-loaded with the most critical information first.

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 zero-required-param, read-only tool with no output schema (compensated by an inline return-shape description), the description is nearly complete. It covers behavior and return format. A minor gap: no mention of capture dimensions/scale relative to the canvas, but this is not critical for an obvious screenshot tool, and the sibling-heavy context is handled well.

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?

With only 1 optional parameter at 100% schema description coverage, the schema already documents sessionId's purpose ('Target browser session ID for multi-browser routing'). Description adds nothing about parameters, but does not need to; per rubric, high coverage sets a 3-4 baseline, and the simple schema is fully self-explanatory.

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 a specific verb+resource+format combo: 'Capture the current Cesium map view as a PNG image.' It clearly distinguishes the tool's action (visual capture of the viewport) from siblings like exportScene or getView, making the sibling differentiation implicit but effective.

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 does not explicitly address when to use this tool over alternatives like exportScene, nor does it mention exclusions or prerequisites (e.g., map must be initialized). The action is clear enough that usage context is implied, but there is no explicit guidance or alternative tool naming, capping this at a mid-range score.

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