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

Annotations already declare this is a non-read-only, non-destructive, closed-world mutation, so the bar is lower. The description adds genuinely useful behavior beyond them: null removes the transition and timing is preserved because the transition is centred on the cut. It does not say what happens when the clips do not touch, whether duration is clamped to clip length, or what is returned, leaving real behavioral questions unanswered for a mutation tool.

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 placement rule and the removal/timing notes are front-loaded and well written, but roughly three quarters of the text is a verbatim re-listing of enum values already fully enumerated in the schema. The category grouping has some selection value, yet the raw enumeration is redundant bulk.

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 4-parameter mutation with no output schema, the description covers placement, valid types, removal, and timing behavior. It stops short of failure modes (non-touching clips, clips too short for the requested duration), which an agent would want before calling.

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 75%, so the description needs to contribute. It does add meaning the enum alone lacks by grouping the 58 values into Basic/Wipes/Push-and-slide/Shapes/Stylized and by explaining that null is the removal signal. It says nothing about duration semantics (interaction with clip lengths, clamping at the 2s max), which is the undocumented parameter in practice.

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 and resource plus the exact placement rule: a transition into a clip from the immediately preceding clip on the same video track, which must touch. That constraint alone distinguishes it from the sibling set_transitions_all and makes the operation unambiguous without opening the schema.

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 a clear precondition for use (two touching clips on the same track) and an explicit removal path ('type null removes it'). It never names set_transitions_all or explains when to apply one transition versus all, which is the main remaining gap.

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