Something suddenly happens (experimental)

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

With no annotations, the description carries the full burden. It usefully discloses ordering semantics (perception resolves before the next character acts) and that the target must be a *running* scene, but says nothing about whether the event is persisted into scene history, whether it consumes a turn, or what comes back from the call.

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?

Two sentences, purpose and examples front-loaded, usage trigger second. No filler and nothing repeated from the schema or title.

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 two-parameter scene-mutation tool with no annotations or output schema, the definition covers what it does, when to call it, and how the result is perceived in-scene. The remaining gap is the effect on scene state and turn ordering beyond the immediate perception rule.

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 both parameters are already documented, including the kebab-case scene id from character_meet. The examples of 'what' do clarify the expected granularity of an event, which is modest added value beyond the schema's 'What happens, in English.'

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 concrete verb and object — 'Adds a sudden change to a running scene' — and immediately grounds it with three examples (cable snaps, voice in the shaft, door opens). The effect on the scene ('everyone present perceives it before the next character acts') separates it from ordinary turn-advancing siblings without needing to name them.

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 an explicit trigger: 'Use when the user asks for a twist mid-scene.' That is a clear when-to-use condition, but there are no when-not conditions and no named alternative (e.g. what to use for ordinary dialogue beats), so routing for edge cases is left to inference.

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