capture_viewport

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

Annotations already declare readOnlyHint=true, and the description adds critical behavioral context: it renders the editor preview only, with scripts/physics/animation NOT running. This clarifies the interpretation of the screenshot and prevents the agent from expecting runtime state. No contradiction with 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?

Four sentences, each earning its place: definition, tip, key rendering note, and when-not-to-use. The most important scoping constraint (editor preview, no runtime) is prominent.

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 parameterless read-only tool with an output format and clear constraints, the description covers what it returns (WebP screenshot), when to use it, prerequisites (focus_viewport), limitations (no scripts/physics/animation), and the alternative (capture_runtime). Nothing needed from an output schema because the tool's output is self-describing.

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 input schema has zero parameters and 100% coverage, so there is nothing to document. Per the zero-parameter baseline this is a 4; the description appropriately focuses on behavior rather than params.

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?

States the verb 'Capture', the resource 'editor viewport', the output format 'downscaled WebP image', and the purpose 'visual verification of edit-time state'. Explicitly distinguishes from capture_runtime by naming the runtime behavior alternative, so an agent can differentiate it from the sibling.

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?

Provides a direct when-not-to-use with the alternative tool: 'use capture_runtime after launch_start'. Also gives a tip to call focus_viewport first to frame entities, providing clear usage context.

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