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set_niagara_user_parameter

DestructiveIdempotent

Sets a user-exposed parameter default on a Niagara System, adding it under the User. namespace if missing, then verifies by reading back.

Instructions

Sets a user-exposed parameter default on a Niagara System's exposed store. Adds the parameter (under the User. namespace) if it does not yet exist, sets the value, then reads it back to verify. Supports float/vector(vec3)/vec2/vec4/color/bool/int. Type is taken from the optional type hint; if omitted, vector key implies Vector and otherwise Float (back-compat). Color is FLinearColor and bool is FNiagaraBool.

Returns: { system_path: string, parameter_name: string, parameter_type: string, value_set: bool, value_read_back?: number|bool|[number...], verified: bool }

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
typeNoOptional type token: Float|Vector|Vec2|Vec4|Color|Bool|Int (case-insensitive). Defaults to Vector if a ``vector`` key is present, else Float
vec2NoOptional [X, Y] for a Vec2 parameter
vec4NoOptional [X, Y, Z, W] for a Vec4 parameter
colorNoOptional [R, G, B, A] (linear) for a Color parameter
valueNoOptional float scalar (Float), int (Int) or bool (Bool) value, per the resolved type
vectorNoOptional [X, Y, Z] for Vector (also implies type=Vector when type omitted)
system_pathYesAsset path of the Niagara System.
parameter_nameYesUser parameter name (without the "User." prefix).

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv1.2.0
    • changedInput schema / required
      Previous value: -[
-  "parameter_name"
-]New value: +[
+  "system_path",
+  "parameter_name"
+]
  2. First observedv1.1.0

TDQS

A3.8/5.0
Behavior4/5

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

Annotations cover the safety profile (not readOnly, idempotent, destructive). The description adds real behavioral context beyond them: it creates the parameter if missing, sets then reads back to verify, and documents type-resolution/back-compat rules. It does not spell out what the destructive mutation touches, but it is well above what the annotations alone convey.

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?

Front-loaded with the core action, then type rules, then an explicit return-shape line. Dense but every sentence carries information; the inline Returns object is useful given no output schema. Minor density on the type-resolution sentence.

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

Completeness4/5

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

For an 8-parameter mutation tool with no output schema, the description supplies the return shape inline and explains type resolution and the add/set/verify sequence. Lacks explicit precondition on asset existence, but otherwise complete enough to invoke correctly.

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

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3, but the description adds genuine meaning: the type hint resolution (vector key implies Vector, else Float for back-compat) and the mapping of Color to FLinearColor and Bool to FNiagaraBool. This clarifies how the loosely-typed value/vec2/vec4/color params resolve, which the schema only partly conveys.

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?

States a specific verb and resource: 'Sets a user-exposed parameter default on a Niagara System's exposed store.' The resource (user parameter default on a system's exposed store) is distinct from component-level setters, but no sibling is explicitly named to sharpen the boundary against get_niagara_user_parameter or the set_niagara_component_* family.

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

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage by describing the write-then-verify flow, but never states when to prefer this over the component parameter setters or the get_niagara_user_parameter reader. No explicit when-not or precondition (e.g., system must exist) is given.

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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