vfx_preview

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

With no annotations, the description carries the full burden and does substantial work: it discloses the TimeScale 0 freeze, that TimeScales are restored afterward, how burst (Enabled false) versus enabled emitters emit, and that the camera auto-frames unless camera_position/look_at_position are supplied. It does not cover permissions, whether the viewport state is otherwise disturbed, or failure behavior, which keeps it below 5.

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?

Four dense sentences, each carrying distinct information (action, emitter timing rules, camera behavior, cleanup), with the main action front-loaded. No filler sentences.

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?

There is no output schema, and the description does not say what the captured images are returned as (paths, base64, a viewer handle) or how multiple moments map to results. Everything else an agent needs for a 6-parameter, 1-required tool is present, so this is one real gap rather than a general shortfall.

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 50%, yet the description explains the semantics of the under-documented parameters: 'at' as the moments after emit, 'emit' as a per-burst override of EmitCount, 'targets' as emitters at or under the given paths, and that camera_position/look_at_position override auto-framing. Only studio_id is left to the schema, which documents it adequately.

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 chain and resource: plays ParticleEmitters under targets in the Edit viewport, freezes them at each moment, and captures one screen image per moment. That is far more specific than a restated name and clearly separates it from siblings like vfx_upload or vfx_delete. It never explicitly distinguishes itself from the closest siblings (vfx_render, vfx_viewer), so it falls short of 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 statement of when to choose this tool over vfx_render or vfx_viewer, no precondition for calling it, and no exclusion. The only usage signal is the implicit 'Edit viewport' / open-Studio requirement, which the agent has to infer from the studio_id parameter.

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