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

Annotations only declare readOnlyHint=false; the description adds non-obvious mutation behavior: later b-roll tracks draw over earlier ones for picture-in-picture, and overlapping placements are refused with the conflicting range. It does not mention permission prerequisites or return shape, which keeps it below 5.

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?

Two dense sentences, front-loaded with the core operation, and each clause conveys track selection, PiP layering, or overlap handling. There is no filler.

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 output schema and only a readOnlyHint annotation, it covers the key behavioral edge cases: overlap refusal, track targeting, and layering. It could still say more about prerequisites or the response, but it is sufficient to invoke correctly.

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 60%, with track_id, project_id, and duration_ms documented. The description adds meaning for otherwise undocumented asset_id and start_time_ms by framing them as asset placement at a position, and clarifies the track_id default plus layering semantics.

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?

States a specific verb ('Place') and resource ('existing video/image asset on a b-roll track at a position'), and clarifies default-vs-named track selection plus picture-in-picture draw order. This clearly distinguishes it from audio, scene, sticker, and text-overlay placement 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?

Explains the default first b-roll track versus a named track and gives an explicit fallback on overlap: re-place or stack on another track. It stops short of naming sibling alternatives such as add_audio_to_timeline or move_clips_to_track, so it is clear context rather than fully explicit when-vs-alternative guidance.

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