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

Annotations already declare readOnly=true, idempotent=true and destructive=false, so the safety profile is covered. The description still adds useful context: cost ('Free'), the no-side-effects guarantee in plain language, and the adaptive stepping behavior with user-visible notice when more than 100 frames would be produced.

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?

Three tight clauses: what you get, how frames are sampled, and when to use it. The purpose is front-loaded and nothing is redundant; even the short 'Free; nothing changes' fragment carries decision-relevant information.

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 three-parameter read-only preview tool with a fully documented schema and no output schema, this covers purpose, sampling behavior, cost, and workflow placement. The only small gap is that it never states explicitly that an image is returned, though 'on one picture' implies it.

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%, so the baseline is 3, and the description adds meaning beyond the schema by explaining the 100-frame widening rule, which directly informs how every_seconds is chosen. It also restates the sensible default of 1 second without adding much new, but the frame-cap behavior is genuine added value.

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 states a specific verb and resource — viewing the whole finished Editor render as a single picture of sampled frames — and specifies the output layout (left to right, top to bottom). This is immediately distinguishable from siblings like frame_at (single frame) or export_editor_project (the render 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?

It gives an explicit trigger: 'Look at it before you call a render done.' That tells the agent exactly where in the workflow this belongs. It stops short of naming alternatives or stating when not to use it, but the review-before-finishing context is unambiguous.

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