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niagara_set_system_user_parameter

Set or update an exposed Niagara System user parameter in Unreal Engine by specifying system path, parameter name, type, and value.

Instructions

Add or update a Niagara System exposed user parameter.

KB: see knowledge_base/09_NIAGARA_VFX.md#overview Example: niagara_set_system_user_parameter(system_path="/Game/MCP_Test/Example", parameter_name="ExampleName")

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
saveNo
valueNo
system_pathYes
parameter_nameYes
parameter_typeNofloat

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.0.0

TDQS

C2.7/5.0
Behavior2/5

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

No annotations are present, so the description carries the full burden of behavioral disclosure. It reveals that the operation adds or updates a parameter, but it does not explain side effects such as asset persistence, whether existing parameters are overwritten, how the save flag behaves, or what 'exposed' means operationally.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact and front-loaded with the core verb and resource. The KB reference and single example are useful and non-redundant. It could be slightly better structured with parameter explanations, but it wastes little space.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 5-parameter mutation tool with no annotations and zero parameter documentation, this description is not complete enough for reliable invocation. The agent is left without guidance on data types, defaults, required parameter interactions, or operational prerequisites, despite an output schema being present.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

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, but it only illustrates system_path and parameter_name via example. The value, parameter_type, and save fields are left completely unexplained; an agent cannot determine valid value formats or how parameter_type affects the operation.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific action ('Add or update') targeting a specific resource ('Niagara System exposed user parameter'). The example showing system_path and parameter_name reinforces the operation. It is distinguishable from siblings like niagara_set_spawn_rate, though 'exposed user parameter' is slightly ambiguous without domain knowledge.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

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 tool versus alternatives such as niagara_apply_system_settings, niagara_describe_system, or niagara_set_fixed_bounds. The KB link and example imply context but provide no conditions, exclusions, or decision rules.

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

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