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

Annotations already declare readOnlyHint=true, openWorldHint=false and idempotentHint=false, so the safety profile is covered. The description adds useful behavior the annotations don't: markers are orange, they can carry labels, and the call ends by showing the drawing (i.e. it returns a rendered image rather than data). It does not disclose that existing markers are discarded unless `add` is set, nor how the rendered output is returned.

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?

One short sentence with the action front-loaded and the render step trailing, plus a parenthetical example. Nothing is redundant and nothing needs trimming.

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?

With four parameters and no output schema, the description carries moderate burden. "then show it" gestures at the returned image but doesn't say what the agent gets back or whether prior markers/measurement lines persist — a meaningful gap given `add` defaults to false and the tool is non-idempotent.

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 75%, so the baseline is 3, and the description justifies a small bump by framing the core output as 'labelled orange markers', which anchors `points` and `labels`. It still does not explain how label strings map to point indices, or when to choose px vs world coordinates — both left to the schema.

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?

Specific verb + resource: "Put labelled orange markers on the drawing" plus the follow-up "then show it", which tells the agent the call also renders the result. It is distinguishable from siblings like `measure` (measurement lines) and `inspect`/`look`, though the description never names those alternatives itself.

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?

"e.g. to point out findings" gives one motivating use case, which implies this is the annotation/pointing-out tool in the family. There is no guidance on when not to use it, no mention of `clear` for removing markers, and no statement of prerequisites (e.g. that a drawing must already be viewed).

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