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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds the operation types (trim/extend/split), which is useful but does not disclose behaviors like revision-based concurrency or potential side effects beyond what annotations already indicate.

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 two concise sentences that are front-loaded with the most important information. Every word contributes, with no redundant or vague phrasing.

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 the complexity of the schema (nested operation union) and the presence of an output schema, the description is minimally adequate. It covers the core behavior but omits important context, such as the need for expectedRevision for optimistic concurrency and how this tool relates to timeline_edit_preview (apply vs preview).

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 50%, with projectId and expectedRevision described. The tool description adds meaning by naming the two operations (trim/extend and split), which helps interpret the 'operation' union parameter. However, it does not explain parameters like trimStartDeltaSeconds, splitAtSeconds, or idempotencyKey, leaving gaps.

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 function with specific verbs and resources: 'Trim or extend one timeline item' and 'Split one timeline item at an exact sequence position.' It distinguishes two operation types and explicitly targets a single timeline item, making it easy to differentiate from siblings.

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?

The description provides clear context on when to use the tool: when you need to trim, extend, or split a single timeline item. However, it does not explicitly mention alternatives or exclusions (e.g., batch edits or previewing), so it falls short of a 5.

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