What the canvas shows

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

Annotations already mark it read-only, idempotent, and non-destructive. The description adds value by specifying exactly what data is fetched (canvas presence, scene, view, targets) and the fact it reflects the Gamemaster's browser. It also notes the dependency relationship with sibling tools. No contradictions 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?

The description is two sentences: the first enumerates the returned information, the second provides usage direction. It is front-loaded with the core purpose and has no redundant text. Efficient and well-structured.

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-parameter read tool, the description is remarkably complete: it enumerates all the data fields returned, names the dependent tools, and conveys the Gamemaster-specific context. Although there's no output schema, the description itself serves as a sufficient guide. It fits the tool's low complexity.

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?

No parameters exist, so the schema fully covers them (100% coverage). The baseline for 0-param tools is 4, and the description doesn't need to add parameter details. It adequately describes the tool's behavior without mentioning parameters.

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 tool reads the canvas state: whether a canvas is drawn, which scene is active, view position/zoom, and targets. It distinguishes itself from siblings by naming pan-camera, ping-canvas, and set-targets as consumers. No ambiguity about what it does.

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?

It explicitly instructs to call this before pan-camera, ping-canvas, or set-targets, which require the canvas. This gives clear when-to-use context. No exclusions, but the primary use cases are well-defined.

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