Example animation for Flare project file.

circle_translation_animation.flr2d.js

{
    "artboards": {
        "type": "artboards",
        "id": 985,
        "name": "Artboards",
        "main": 0,
        "children": [{
            "type": "artboard",
            "id": 986,
            "name": "Artboard",
            "translation": [0, 0],
            "origin": [0.5, 0.5],
            "width": 1024,
            "height": 768,
            "color": [0.364705890417099, 0.364705890417099, 0.364705890417099, 1],
            "clipContents": true,
            // artboards can have a list of animations
            "animations": [{
                "displayEnd": 10, // start of the visible area (this is an editor settings/optional)
                "displayStart": 0, // end of the visible area (this is an editor settings/optional)
                "duration": 10, // duration of the entire animation in seconds (defines the end in terms of what can be scrolled/zoomed to)
                "fps": 60, // frame rate used only to round to the closest whole frame while placing keyframes
                "id": 9000,
                "isWorkAreaActive": true, // whether the work area is turned on
                "loop": false, // whether the animation loops
                "name": "Untitled", // name for this animation
                "order": -1, // order in the animation list
                "nodes": { // map from node id to map of animated properties
                    "987": { // node with id 987
                        "framePosX": // key is the property to animate (in this case x translation)
                        [ // value is a list of keyframes
                          {
                            "t": 0, // time
                            "v": 0, // value
                            "i": 2, // interpolation type cubic
                            "curve": [0.42, 0, 0.58, 1] // easing parameters for interpolation
                          }, {
                            "t": 1.0833333333333333, // time
                            "v": 300, // value
                            "i": 1 // linear
                          }
                        ]
                    }
                },
                "position": 1.0833333333333333,
                "workAreaEnd": 1.0833333333333333,
                "workAreaStart": 0.3
            }],
            "children": [{
                "type": "shape",
                "id": 987,
                "name": "Ellipse",
                "blendMode": "srcOver",
                "drawOrder": 1,
                "children": [{
                    "type": "colorFill",
                    "id": 989,
                    "name": "Color",
                    "opacity": 1,
                    "color": [1, 0, 0, 1],
                    "fillRule": "nonzero"
                }, {
                    "type": "ellipse",
                    "id": 990,
                    "name": "Ellipse Path",
                    "width": 100,
                    "height": 100
                }]
            }]
        }]
    },
    "settings": {}
}

Animatable properties:

// Node
framePosX
framePosY
frameScaleX
frameScaleY
frameRotation
frameOpacity
// Drawable
frameDrawOrder
// Bone
frameLength
// Image
frameImageVertices
// Constraint
frameStrength
// Event
frameTrigger
// Custom Properties
frameIntValue
frameFloatValue
frameStringValue
frameBooleanValue
// Solo
frameActiveChild
// Path
framePathVertices
// Fill
frameFillColor
frameFillGradient
frameFillRadial
// Stroke
frameStrokeColor
frameStrokeGradient
frameStrokeRadial
frameStrokeWidth
frameStrokeOpacity
frameFillOpacity
// Procedural Path
frameWidth
frameHeight
// Rectangle
frameCornerRadius
// Star
frameInnerRadius
// Trim
frameStrokeStart
frameStrokeEnd
frameStrokeOffset

Interpolation types:

0 - Hold
1 - Linear
2 - Cubic

Example can be seen here:
https://www.2dimensions.com/a/castor/files/flare/circle-translation-animation