# AggregationDecl

One aggregation function declaration.

**Type**: `object`

## Properties

- name: args (optional)
  type: array of object
  description: Function arguments. Heterogeneous; validated at pipeline construction. PERCENTILE accepts [rank], [rank, relativeAccuracy], or [rank, relativeAccuracy, maxNumBins].

- name: as (optional)
  type: string
  description: Output suffix. Omitted = preserve source metric name; in rule conditions the output is addressed as `<alias>.val` (at most one as-less aggregation per block).

- name: fn (required)
  type: `AggType`