MCP: XYChartConfig has no sort option — bar charts created via MCP are always ordered by category name

[DanRoscigno]

Problem

XYChartConfig in superset/mcp_service/chart/schemas.py (line 1662 on master @ 7b351d5) exposes no way to order categories. Its full field set is:

chart_type, x, y, kind, time_grain, orientation, stacked, group_by,
x_axis, y_axis, legend, x_axis_time_format, show_value, currency_format,
color_scheme, filters, row_limit, series_limit

There is no sort field, and grep -ci sort over the class body returns 0.

Other chart configs in the same file do have one:

• TableChartConfig — sort_by: List[str | SortByConfig] (line 1572)
• PieChartConfig — sort_by_metric: bool = True (line 1047)

A SortByConfig model already exists (line 997) with column and ascending fields, and its docstring describes exactly the relevant use case:

Bare strings default to descending, which matches the
sort-by-metric "top N" pattern most commonly used for tables.

Effect

Every xy chart created through MCP is emitted with:

"x_axis_sort_series_type": "name",
"x_axis_sort_series_ascending": true

so categorical bar charts are always ordered by category name. For a ranking — the most common reason to reach for a bar chart — this is the wrong default and there is no way to override it through the tool. The equivalent is a one-click "Sort by metric" toggle in the Explore UI, so charts built via MCP start out worse than charts built by hand and need manual fixing afterwards.

Concrete case: a bar chart of orders per Brazilian state (27 categories, top value ~3x the second and ~900x the smallest) renders alphabetically AC, AL, AM, AP, BA… The concentration that motivates the chart is invisible until a human re-sorts it.

Sorting is also not reachable by other means, since update_chart accepts only the simplified config (raw form_data is not honoured), and unknown nested keys such as x_axis: {"sort_by": ...} are silently dropped rather than rejected (filed separately).

Proposed change

Add a sort field to XYChartConfig, reusing the existing SortByConfig:

sort_by: SortByConfig | None = Field(
    None,
    description="Order categories by a metric label or column. "
                "Defaults to category name when unset.",
)

mapping to the native x_axis_sort / x_axis_sort_asc (or x_axis_sort_series_type / x_axis_sort_series_ascending for the series case) form_data keys.

Two things worth deciding in review:

1. Whether to change the default. Leaving it at category-name ordering is the compatible choice; defaulting bar charts to metric-descending matches what people usually want but would alter existing charts on regeneration. I'd lean toward keeping the current default and making sort opt-in.
2. Scope. kind covers line, bar, area, scatter. Sorting is meaningful for categorical bar/area but not for a temporal x-axis, so it may warrant a validator rejecting sort_by when time_grain is set.

Happy to implement whichever shape reviewers prefer.

Environment

• Apache Superset 6.1.0 (docker), pydantic 2.11.7, fastmcp 3.4.5
• Field lists confirmed against master @ 7b351d5

[DanRoscigno]

Cross-referencing #42626 / #42628: the reason this surfaced as a silent no-op rather than an error is that unknown keys nested inside x_axis were being dropped by extra="ignore". With that fixed, x_axis: {"sort_by": ...} will at least fail loudly — but there is still no supported way to sort an xy chart, which is what this issue tracks.

[sadpandajoe]

@aminghadersohi is this something on your roadmap?