xfade_transition

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

With no annotations, the description carries the full burden and does well: it discloses that both inputs are auto-normalized to a common resolution, fps, and audio rate, that offsets follow each clip's video length, and that missing audio is replaced with silence. It does not mention overwrite behavior or where output lands, though those are covered by the schema.

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 tight sentences, front-loaded with the core action followed by the two non-obvious behaviors. Nothing redundant, though the last sentence is dense enough that it reads slightly like a spec dump.

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 media-transformation tool with full schema description coverage, the description supplies exactly the non-obvious runtime facts an agent needs (auto-normalization, offset basis, audio fallback). Overwrite and output defaults are handled in the schema, so nothing material 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 100%, so the baseline is 3. The description adds real meaning beyond the schema by explaining that offsets are computed from each clip's video length and that normalization makes mismatched inputs acceptable, which clarifies how duration and the two input paths actually interact.

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 ('Crossfade two videos into one with an xfade transition') and the key distinguishing behavior from concat (a blended transition rather than a hard join). An agent can tell what this produces 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?

Usage is implied by the description — you use it when you want a crossfade rather than a hard cut — but the description never names the alternative sibling (concat) or states when a crossfade is inappropriate (e.g., mismatched content, very short clips). No exclusions or prerequisites are given.

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