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

With no annotations provided, the description carries the full burden and does so thoroughly. It discloses that contents are not mutated, that writing a window overrides the derived contents-hull, and that two safety corrections (keyframesCompensatedBy and grownToCoverKeyframes) happen automatically. It also names the reported fields despite the lack of an output schema.

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 detailed but every sentence earns its place: it front-loads the core action, explains what it does not do, states the intended use, describes automatic safety behavior, and points to the relevant sibling. No filler or repetition is present.

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 mutation tool with no annotations and no output schema, this description is unusually complete. It explains the behavioral effect, the safety corrections, the reported fields, and the main alternative. The agent has enough context to call it correctly without further inference.

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?

The input schema already provides full descriptions for all four parameters, so the baseline is 3. The description adds meaningful semantics beyond the schema by explaining how start and duration define a visible window, how duration can be grown to avoid hiding keyframes, and how start changes trigger keyframe compensation. This enriches the agent's understanding without being redundant.

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 opens with a specific verb and resource: 'TRIM a group's own visible window' with an explicit range definition. It distinguishes this tool from shift_group by clarifying that contents are NOT moved or deleted, making its purpose unmistakable.

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 clearly states when to use this tool: 'use it to hide the head or tail of a whole section.' It explicitly names the alternative for moving contents: 'To MOVE the group and its contents instead, use shift_group.' This gives the agent actionable selection criteria.

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