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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered; the description adds real value by disclosing a behavioral limitation ('Physical DPI is unknown') so the agent won't attempt a DPI-dependent path. It does not mention cost, size limits, or freshness constraints of the returned snapshot, which keeps it short of a 5.

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 short sentences, front-loaded with the verb and the returned field set, followed by the one caveat that matters. No filler or restatement of the title.

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?

Because there is no output schema, enumerating the returned fields is necessary and it is done adequately, and the DPI caveat is a genuine completeness win. However, for a tool whose results include component summaries, nothing is said about result size, truncation, or whether a canvas must be claimed/pairing established first — both relevant given siblings like claim_canvas and pairing_status.

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 description coverage is 0% for the single required parameter 'controlToken', and the description never mentions it — no hint that it identifies the paired/claimed canvas session or where to obtain it. With one undocumented parameter the description bears the burden and does not compensate.

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 a specific verb ('Reads') and enumerates the concrete canvas state fields returned (revision, focus, component summaries, render status, media capabilities, display dimensions). This reasonably separates it from write-oriented siblings like update_component or publish_draft, but it never explicitly contrasts with the other read siblings (read_component, inspect, get_console).

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 statement of when to call this rather than read_component, inspect, or get_console, nor any precondition such as needing a claimed canvas first. Usage is only inferable from the fact that it is a 'Reads' tool.

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