fgui_update_transition_item

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

There are no annotations, so the description carries the full disclosure burden. It discloses that the operation replaces/overwrites an existing item and explicitly notes it can be undone with fgui_undo/redo. It does not explain behavior on invalid index, validation rules, or whether a save step is required afterward.

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 description is a single short sentence that front-loads the action and target, then adds a helpful undo note. It is concise and free of filler, though its brevity leaves important parameter context unaddressed.

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?

With all 3 parameters required, one deeply nested item object, and no annotations, the description is too sparse to fully guide an agent. The output schema exists so return values need not be explained, but the meaning of 'name' and the structure of the replacement item are essential and 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 0%, so the description must compensate. It only maps '指定索引' to item_index and '关键帧项' to item, but does not explain the required 'name' parameter or how to construct the complex TransitionItem value. Most parameter semantics remain unspecified.

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 clearly states the action: '替换' (replace) the keyframe item at a specified index of a Transition. This distinguishes it from add/remove/upsert transitions, though it does not name a sibling explicitly.

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 wording implies use when modifying an existing keyframe item at a known index, and the undo mention adds practical guidance. However, there is no explicit comparison to fgui_add_transition_item or fgui_remove_transition_item, and no prerequisites such as needing an open document or existing transition.

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