gdalinfo json format

gdalinfo

{
    "driver": "GTiff/GeoTIFF",
    "files": [
        "../gcore/data/byte.tif",
        "../gcore/data/byte.tif.aux.xml"
    ],
    "size": [
        20,
        20
    ],
    "coordinateSystem": {
        "proj": "+proj=.......",
        "wkt": "PROJCS[....]"
    },
    "gcp": {
        "proj": "PROJCS[...",
        "gcpList": [
            {
                "id": "1",
                "info": "a",
                "pixel": 0.5,
                "line": 0.5,
                "X": 0.0,
                "Y": 0.0,
                "Z": 0.0
            }
        ]
    },
    "origin": [
        440720.000000000000000,
        3751320.000000000000000
    ],
    "pixelSize": [
        60.000000000000000,
        -60.000000000000000
    ],
    "metadata": {
        "AREA_OR_POINT": "Area"
    },
    "imageStructureMetadata": {
        "INTERLEAVE": "BAND"
    },
    "cornerCoordinates": {
        "upperLeft": [
            440720.000,
            3751320.000
        ],
        "lowerLeft": [
            440720.000,
            3750120.000
        ],
        "upperRight": [
            441920.000,
            3751320.000
        ],
        "lowerRight": [
            441920.000,
            3750120.000
        ],
        "center": [
            441320.000,
            3750720.000
        ]
    },
    "bands": [
        {
            "band": 1,
            "block": [
                20,
                20
            ],
            "type": "Byte",
            "colorInterp": "Gray",
            "min": 74.000,
            "max": 255.000,
            "computedMin": 74.000,
            "computedMax": 255.000,
            "minimum": 74.000,
            "maximum": 255.000,
            "mean": 126.765,
            "stdDev": 22.928,
            "overviews": [
                {
                    "size": [
                        400,
                        400 ],
                    "checksum": X (if -checksum specified)
                }, 
                { "size": [
                        200,
                        200 ],
                    "checksum": X (if -checksum specified)
                }
            ],
            "metadata": {
                "STATISTICS_MAXIMUM": "255",
                "STATISTICS_MEAN": "126.765",
                "STATISTICS_MINIMUM": "74",
                "STATISTICS_STDDEV": "22.928470838676"
            },
            "histogram": {
                "count": 25,
                "min": -0.5,
                "max": 255.5,
                "buckets": [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
            },
            "checksum": 4672,
            "colorTable": {
                "palette": "RGB",
                "count": 6,
                "entries": [
                    [255,255,255,255],
                    [255,255,208,255],
                    [255,255,204,255],
                    [153,204,255,255],
                    [0,153,255,255],
                    [102,102,102,255]
                ]
            }
        }
    ]
}

I'd encourage you to remove the spaces from the key strings (CoordinateSystem, CornerCoordinates, ... would be better). Actually in JSON, keys are generally with camelCase convention, so coordinateSystem, cornerCoordinates, etc...
For coordinateSystem, you could have a dictionary like

"coordinateSystem": {
"proj": "+proj=.......",
"wkt": "PROJCS[....]"

Yes the full WKT string is a string that cannot easily been represented more naturally as a JSon objet. In your example, I think you might have quoting issues by the way due to the presence of " inside WKT itself.

Metadata should be represented as JSON dictionary.
"metadata" : {
"KEY1": "value1",
"KEY2":"value2
}