fix(mcp): clarify chart preview URL metadata by richardfogaca · Pull Request #39731 · apache/superset

richardfogaca · 2026-04-28T16:34:47Z

SUMMARY

Clarifies MCP chart preview metadata and guidance now that URL previews return interactive Explore links rather than static screenshot image URLs.

This follow-up to #39719 updates:

URLPreview width/height descriptions to refer to requested Explore viewport dimensions
URLPreview.supports_interaction to default to true
chart preview tool guidance/docstrings so clients see the supported ASCII, URL, table, and Vega-Lite formats

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Not applicable; MCP schema/documentation metadata only.

TESTING INSTRUCTIONS

PYENV_VERSION=superset pre-commit run --files superset/mcp_service/app.py superset/mcp_service/chart/schemas.py superset/mcp_service/chart/tool/get_chart_preview.py tests/unit_tests/mcp_service/chart/tool/test_get_chart_preview.py
PYENV_VERSION=superset pytest tests/unit_tests/mcp_service/chart/tool/test_get_chart_preview.py -q

ADDITIONAL INFORMATION

Has associated issue:
Required feature flags:
Changes UI
Includes DB Migration (follow approval process in SIP-59)
- Migration is atomic, supports rollback & is backwards-compatible
- Confirm DB migration upgrade and downgrade tested
- Runtime estimates and downtime expectations provided
Introduces new feature or API
Removes existing feature or API

codecov · 2026-04-28T17:00:06Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.49%. Comparing base (4b42f82) to head (1c90a48).
⚠️ Report is 9 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #39731      +/-   ##
==========================================
- Coverage   64.49%   64.49%   -0.01%     
==========================================
  Files        2566     2566              
  Lines      133960   133958       -2     
  Branches    31116    31115       -1     
==========================================
- Hits        86394    86392       -2     
  Misses      46071    46071              
  Partials     1495     1495

Flag	Coverage Δ
hive	`39.74% <100.00%> (ø)`
mysql	`60.19% <100.00%> (ø)`
postgres	`60.27% <100.00%> (ø)`
presto	`41.51% <100.00%> (ø)`
python	`61.83% <100.00%> (ø)`
sqlite	`59.90% <100.00%> (ø)`
unit	`100.00% <ø> (ø)`

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Copilot

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Updates MCP chart preview metadata/documentation to reflect that URL previews now return interactive Explore links (not screenshot image URLs), and clarifies the available preview formats.

Changes:

Update URLPreview schema descriptions for width/height and default supports_interaction=True
Refresh tool docstring and MCP default instructions to describe supported preview formats (ASCII/URL/table/Vega-Lite)
Adjust unit tests to expect Explore URLs and interactive defaults

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
tests/unit_tests/mcp_service/chart/tool/test_get_chart_preview.py	Updates expectations to Explore URL format and interactive default.
superset/mcp_service/chart/tool/get_chart_preview.py	Revises docstring to describe supported preview output types beyond screenshots.
superset/mcp_service/chart/schemas.py	Clarifies URL preview metadata and defaults `supports_interaction` to true.
superset/mcp_service/app.py	Updates general MCP instructions to reflect new chart preview output options.

aminghadersohi

Review by Claude (AI assistant) on behalf of @preset-io/amin

Thanks for the cleanup! A few things worth discussing before this merges:

Scope of PR: The description says "schema/documentation metadata only" but the diff includes API-breaking field removals from ChartInfo (owners, changed_by, created_by), a new sanitization_warnings field + model validator on GenerateChartRequest, and a change to the exception handler in a production path. It would help future reviewers and changelog readers to call these out explicitly in the summary.

Exception narrowing (get_chart_preview.py, outer except clause): The original except Exception ensured callers always received a structured ChartError. The new explicit union omits IndexError, RuntimeError, PermissionError, etc. An unexpected exception type will now propagate unhandled. Consider either restoring the catch-all with an inner isinstance guard for re-raise, or adding Exception as a final catch with a distinct log level for unexpected types.

Default format change: GetChartPreviewRequest.format silently changes default from "url" to "ascii". Clients relying on the default will now get different output. Worth a note in SUMMARY and UPDATING.md if this is intentional.

created_by_fk removal: Any client currently passing {"col": "created_by_fk", ...} to list_charts will get a Pydantic validation error instead of results. If removing this is intentional for privacy, a migration note ("use search parameter instead") would help.

Test host: Copilot's comment about localhost:8088 in the unit test is valid and easy to fix — the dimension test a few lines below already uses example.com.

None check after typed required field (get_chart_preview.py): The if request.identifier is None guard is dead code — identifier is typed int | str and marked required, so it can never reach that branch.

The privacy guardrails (app.py instructions, ChartInfo field removals) are well-designed and appropriate. The GenerateChartRequest aliases and sanitization_warnings design are reasonable. The main blocker is the exception handler regression.

bito-code-review · 2026-04-28T22:34:12Z

Code Review Agent Run #9e46a0

Actionable Suggestions - 0

Review Details

Files reviewed - 4 · Commit Range: 80c52f1..80c52f1
- superset/mcp_service/app.py
- superset/mcp_service/chart/schemas.py
- superset/mcp_service/chart/tool/get_chart_preview.py
- tests/unit_tests/mcp_service/chart/tool/test_get_chart_preview.py
Files skipped - 0
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…tadata

richardfogaca · 2026-04-29T00:06:05Z

Thanks @aminghadersohi. I checked #39731 against the current master base, and the broader items you called out appear to come from prior merged MCP changes rather than this PR’s diff.

I pushed 1c90a48 to address the direct test-host issue by replacing the illustrative localhost:8088 URL with example.com.

I agree the exception-handler concern is worth a focused follow-up, but since it predates this metadata cleanup, I’d prefer to handle it separately so this PR stays scoped to the chart preview wording/schema-test updates.

bito-code-review · 2026-04-29T04:25:40Z

Code Review Agent Run #1cd4b5

Actionable Suggestions - 0

Review Details

Files reviewed - 1 · Commit Range: 80c52f1..1c90a48
- tests/unit_tests/mcp_service/chart/tool/test_get_chart_preview.py
Files skipped - 0
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aminghadersohi

Thanks for the quick fix on the test host — is the right call there. Approving; the exception narrowing concern is worth a follow-up but not a blocker given FastMCP's top-level error handling. LGTM otherwise.

aminghadersohi

Thanks for the quick fix on the test host — using example.com is the right call there. Approving; the exception narrowing concern is worth a follow-up but not a blocker given FastMCP's top-level error handling. LGTM otherwise.

fix(mcp): clarify chart preview URL metadata

80c52f1

pull-request-size Bot added the size/S label Apr 28, 2026

richardfogaca mentioned this pull request Apr 28, 2026

fix(mcp): default chart previews to ascii #39719

Merged

9 tasks

richardfogaca self-assigned this Apr 28, 2026

richardfogaca requested a review from aminghadersohi April 28, 2026 17:19

richardfogaca marked this pull request as ready for review April 28, 2026 17:19

Copilot AI review requested due to automatic review settings April 28, 2026 17:19

Copilot AI reviewed Apr 28, 2026

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Comment thread tests/unit_tests/mcp_service/chart/tool/test_get_chart_preview.py Outdated

Comment thread tests/unit_tests/mcp_service/chart/tool/test_get_chart_preview.py Outdated

Copilot started reviewing on behalf of richardfogaca April 28, 2026 17:33

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aminghadersohi reviewed Apr 28, 2026

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richardfogaca and others added 2 commits April 28, 2026 20:54

Merge branch 'master' into richardfogaca/clarify-chart-preview-url-me…

a6d6343

…tadata

test(mcp): use example host for chart preview URL

1c90a48

richardfogaca requested a review from aminghadersohi April 29, 2026 00:06

aminghadersohi approved these changes Apr 29, 2026

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richardfogaca merged commit 549aff7 into apache:master Apr 29, 2026
65 of 68 checks passed

richardfogaca deleted the richardfogaca/clarify-chart-preview-url-metadata branch April 29, 2026 15:37

bestlong pushed a commit to bestlong/superset that referenced this pull request May 7, 2026

fix(mcp): clarify chart preview URL metadata (apache#39731)

232f677

qfcwell pushed a commit to qfcwell/superset that referenced this pull request May 12, 2026

fix(mcp): clarify chart preview URL metadata (apache#39731)

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fix(mcp): clarify chart preview URL metadata - #39731

fix(mcp): clarify chart preview URL metadata#39731
richardfogaca merged 3 commits into
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richardfogaca commented Apr 28, 2026

SUMMARY

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

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