Add Keyframe

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

Annotations already declare a non-read-only, non-idempotent, non-destructive write. The description adds real value beyond them: it discloses that the receipt warns when the keyframe time falls outside the clip's visible range, and it scopes the verification to stored parameter data only.

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 with the action front-loaded and no filler. The trailing scope caveats are brief and each carries information, though the third sentence is slightly dense.

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?

An output schema exists, so return values need no explanation. For a write tool with annotations already covering the safety profile, the description adds the warning behavior and the verification boundary, leaving little an agent needs 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 description coverage is 100%, so all five parameters are already documented in the schema. The description alludes to time semantics ('outside the clip's visible range') but adds no syntax or format beyond what the schema provides, so the baseline 3 applies.

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 ('Add and read back a keyframe on an effect property'), which is distinct from siblings like add_audio_keyframes (audio) and get_keyframes (read-only). It is clear without explicitly naming an alternative.

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 scope note ('verifies stored parameter data only; render/playback verification remains host-dependent') implies the intended context, but it never states when to use this over set_keyframe_interpolation, get_keyframes, or add_audio_keyframes. Usage is inferable, not explicit.

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