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

Annotations already flag non-read-only, non-idempotent, non-destructive behavior, and the description adds real context: a hard 40-scene limit, default insert position at the end, the asset-reference syntax for images, and the demos:read/demos:write scopes required. It doesn't say what happens when the limit is hit or how errors surface.

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 short sentences, front-loaded with the action and mechanism, then constraints, then auth. Every sentence carries information an agent needs; nothing is 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 low schema coverage, the description covers the critical semantics and limits. The remaining gap is the meaning of label/intent/narration (e.g., whether narration auto-generates audio), which an agent may have to infer.

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 only 38%, yet the description compensates for the highest-risk parameters: block's provenance, values as a variable map with the 'asset:<key>' convention for images, and position's default of end. label, intent, narration and durationMs remain undocumented beyond their 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?

A specific verb and resource ('adds a scene') plus the mechanism ('from a motion-kit block') and scope ('up to 40 scenes'). It also names the sibling that supplies block ids (list_video_blocks), so an agent can act without guessing where the block value comes from.

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?

Gives clear preconditions: fetch a block via list_video_blocks first, and note the 40-scene ceiling and required scopes. It stops short of stating when to use update_scene/write_scene/move_scene instead, so the choice among scene-mutating siblings is left implicit.

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