CoplayDev/unity-mcp · error · ValueError

{context} must be a list of colors

Error message

{context} must be a list of colors

What it means

Raised by _normalize_palette (texture.py:152) when the palette value, after optional JSON parsing, is not a list. A palette must be a JSON array of colors. The 'context' label is 'palette' (from the create command's --palette option).

Source

Thrown at Server/src/cli/commands/texture.py:152

                if _is_normalized_color(value):
                    return [int(round(float(c) * 255)) for c in value]
                return [int(c) for c in value]
            except (TypeError, ValueError):
                raise ValueError(
                    f"{context} values must be numeric, got {value}")
        raise ValueError(
            f"{context} must have 3 or 4 components, got {len(value)}")

    raise ValueError(f"{context} must be a list or hex string")


def _normalize_palette(value: Any, context: str) -> list[list[int]]:
    if value is None:
        return []
    if isinstance(value, str):
        value = try_parse_json(value, context)
    if not isinstance(value, list):
        raise ValueError(f"{context} must be a list of colors")
    return [_normalize_color(color, f"{context} item") for color in value]


def _normalize_pixels(value: Any, width: int, height: int, context: str) -> list[list[int]] | str:
    if value is None:
        raise ValueError(f"{context} is required")
    if isinstance(value, str):
        if value.startswith("base64:"):
            return value
        trimmed = value.strip()
        if trimmed.startswith("[") and trimmed.endswith("]"):
            value = try_parse_json(trimmed, context)
        else:
            return f"base64:{value}"
    if isinstance(value, list):
        expected_count = width * height
        if len(value) != expected_count:
            raise ValueError(

View on GitHub (pinned to c21bf496bc)

Solutions

1. Pass the palette as a JSON array of colors, e.g. '["#FF0000","#00FF00"]'.
2. Wrap a single color in brackets: '["#FF0000"]'.
3. Confirm the --palette JSON parses to a list before running.

Example fix

# before
unity-mcp texture create Assets/Tex.png --pattern checkerboard --palette '"#FF0000"'

# after
unity-mcp texture create Assets/Tex.png --pattern checkerboard --palette '["#FF0000","#00FF00"]'

# Python - ensure palette is a list before _normalize_palette
if not isinstance(value, list):
    raise ValueError(f"{context} must be a list of colors")

def is_palette_list(v) -> bool: return isinstance(v, list)

try:
    palette = _normalize_palette(value, context)
except ValueError as e:
    print_error(str(e)); sys.exit(1)

When it happens

Trigger: Passing --palette '"#FF0000"' (a single color string, not an array), --palette '{"a":1}' (a dict), or a JSON string that parses to a scalar. The create command calls _normalize_palette(palette, 'palette').

Common situations: Forgetting the outer array brackets around palette colors; passing a single color where a list is required; a JSON object where an array was intended.

Related errors

• width and height must be positive
• Invalid hex color: {value}
• {context} is required
• {context} dict values must be numeric, got {value}
• {context} values must be numeric, got {value}

AI-assisted analysis of CoplayDev/unity-mcp@c21bf496bc (2026-08-13). Data as JSON: /api/errors/6a0acebd0357766f. Report an issue: GitHub.