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

Annotations already declare readOnlyHint=true, destructiveHint=false, so the read-only nature is known. The description adds valuable behavioral context not in annotations: the requirement that a browser must have the canvas open, and the specific error/retry flow. It does not over-explain.

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 front-loaded with the core purpose, followed by prerequisite, usage context, and error handling. Each sentence contributes meaning, though some information (room_id requirement) is also present in the schema, making it slightly redundant.

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?

Given that an output schema exists and annotations cover safety, the description adequately covers the tool's purpose, prerequisites, related tools, and a key failure mode. It is complete enough for an agent to invoke correctly without further clarification.

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% with descriptions for all parameters, including a detailed room_id extraction pattern. The description only restates that room_id is required and that there are optional filters, adding minimal semantic value beyond the schema. Baseline of 3 is appropriate.

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's purpose: querying elements on a canvas with optional filters. It also distinguishes itself from siblings by explicitly positioning it as a precursor to update_elements for small edits to existing diagrams.

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 explicit usage guidance: requires a room_id from a previous Canvs tool result, should be used before update_elements, and describes the browser-open prerequisite and how to handle the error if the browser is not open. This is well beyond minimal guidance.

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