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

Annotations only provide a title and destructiveHint=false, so the description carries most of the behavioral burden. It discloses deterministic behavior, track inference rules, image still behavior, default position, and that it returns clip_id. It does not explicitly mention auth or side effects, but the tool is non-destructive and the behavior is well covered. The description adds substantial value beyond the annotations, so a 4 is appropriate.

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 a single, dense paragraph that front-loads the core purpose and key behavioral rules. Every sentence earns its place: it gives the action, the deterministic alternative, track inference, position default, and return value. No fluff or repetition.

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 tool's moderate complexity (6 parameters, 2 required) and lacking output schema, the description covers all necessary aspects for correct invocation: what it does, how to use it, parameter defaults, and return value. Sibling tools like 'remove_clip' and 'reorder_clip' are distinct, and the integration with the timeline is clear. Nothing critical is missing.

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 low (17%), so the description must compensate, and it does. It explains the semantics of 'track' (which values map to which tracks), 'position' (default append, 0-based index), 'duration_sec' (only for image stills, default 1), and the role of asset_id and project_id. This adds meaning beyond the schema's bare parameter names.

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 purpose: to place an existing LIBRARY asset onto a video's timeline by id. It distinguishes itself from the sibling 'video_editor_instruct' by explicitly saying to use this instead of asking instruct to 'add a clip'. The verb 'place' and resource 'asset onto timeline' are specific and unambiguous.

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 explicit guidance on when to use this tool: when you have a library asset id and want to add it to the timeline. It also tells the agent to prefer this over 'instruct' for deterministic behavior. It explains track inference, position default, and image duration default, giving clear usage context without needing to inspect the schema.

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