Adjust the f-stop aperture on a CineCameraActor to control depth of field in Unreal Engine 5.
Set the aperture (f-stop) on a CineCameraActor for depth-of-field control.
Returns: { camera_actor_name: string, aperture: number, success: bool }
| Name | Required | Description | Default |
|---|---|---|---|
| aperture | Yes | F-stop value. Must be between 0.01 and 512.0. | |
| camera_actor_name | Yes | Name or label of the CineCameraActor to modify. |
Changes observed during successful MCP inspections.
v1.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=true, so the safety profile is covered structurally. The description adds the return payload shape, which is genuine value since no output schema exists, but it says nothing about persistence, target resolution failures, or what 'success: false' implies, so behavioral disclosure is only partial.
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 compact sentences with the action front-loaded and the return shape isolated on its own line. Nothing is padded, though the return line is stated as a raw type signature rather than in prose an agent can act on.
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 setter with no output schema, the description covers the action, the parameter meaning and the return fields, and annotations carry the mutation/idempotency profile. It stops short of stating execution context (editor vs PIE) or failure modes, which would be the remaining useful additions.
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% — both camera_actor_name and aperture are documented, including the 0.01–512.0 valid range. The description's only extra signal is the parenthetical '(f-stop)', which restates the schema and adds no syntax or format detail, so 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?
Names a specific verb and resource (set aperture/f-stop on a CineCameraActor) and states the intent (depth-of-field control), so the action is unambiguous. However, it does not differentiate itself from close siblings such as set_cine_camera_focal_length, set_cine_camera_focus, set_cine_camera_lens, or set_cine_camera_filmback, which an agent could easily confuse.
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 when-to-use guidance, no prerequisites (e.g. does a CineCameraActor need to exist or be possessed?), and no mention of alternatives among the many cine camera setters. The agent must infer all context from the name alone.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.