design_set_keyframe

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

No annotations are provided, so the description carries the full burden. The phrase "or replace" hints that an existing keyframe at the same time is overwritten, but it does not say whether prior easing/value is lost, whether the call fails if the layer or timeline is missing, or what the call returns.

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?

A single front-loaded sentence with no filler. It is efficient, though for a five-parameter mutation tool the brevity borders on under-specification rather than pure conciseness.

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?

This is a state-mutating tool with three required parameters, no annotations and no output schema. The description leaves unaddressed whether a timeline must already exist, whether the layer must be visible/unlocked, and what happens to a keyframe already at that time.

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 every parameter (layerId, property, time, value, easing) is already documented, including units and the default easing. The description adds nothing beyond that, which makes the baseline 3 appropriate.

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?

The description gives a specific verb pair ("Add or replace") and a specific resource ("a keyframe on a layer property"), which is clearly distinct from siblings like design_remove_keyframe, design_clear_keyframes and design_list_keyframes. It stops short of naming those siblings, so it does not reach a 5.

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?

There is no guidance on when to use this versus design_remove_keyframe, design_clear_keyframes, or design_preview_at, and no prerequisites such as an existing timeline or target layer. The agent must infer the context entirely from the tool name.

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