fix(mcp): cap search_metadata response size to prevent LLM context overflow by Shreyansh100704 · Pull Request #28383 · open-metadata/OpenMetadata

Shreyansh100704 · 2026-05-22T16:51:04Z

Describe your changes:

Added 100k character safety cap on search_metadata responses. When exceeded, results are trimmed and the LLM is guided to narrow the search.
Updated tool schema description to guide LLM toward smaller page sizes for broad queries.

Fixes #28382

Type of change:

High-level design:

N/A — small change.

Tests:

Use cases covered

Unit tests

Backend integration tests

Ingestion integration tests

Playwright (UI) tests

Manual testing performed

UI screen recording / screenshots:

Not applicable.

Checklist:

I have read the CONTRIBUTING document.
My PR title is Fixes #28382: fix(mcp): cap search_metadata response size to prevent LLM context overflow
My PR is linked to a GitHub issue via Fixes #28382 above.
I have commented on my code, particularly in hard-to-understand areas.
For JSON Schema changes: N/A, no schema changes.
For UI changes: N/A, backend only.
Added 3 new unit tests covering trim trigger, no-trim, and floor-of-one cases.

Summary by Gitar

MCP logging & safety:
- Downgraded response size log level to DEBUG to reduce log noise.
- Applied an 0.8 safety factor to the character limit cap for more robust response trimming.
Testing:
- Added testResponseTrimmedWhenExceedingCharLimit and related cases to SearchMetadataAggregationTest to verify payload truncation logic.

_{This will update automatically on new commits.}

github-actions · 2026-05-22T16:51:30Z

Hi there 👋 Thanks for your contribution!

The OpenMetadata team will review the PR shortly! Once it has been labeled as safe to test, the CI workflows
will start executing and we'll be able to make sure everything is working as expected.

Let us know if you need any help!

github-actions · 2026-05-22T16:51:49Z

Hi there 👋 Thanks for your contribution!

The OpenMetadata team will review the PR shortly! Once it has been labeled as safe to test, the CI workflows
will start executing and we'll be able to make sure everything is working as expected.

Let us know if you need any help!

…ming

github-actions · 2026-05-22T17:09:21Z

Hi there 👋 Thanks for your contribution!

The OpenMetadata team will review the PR shortly! Once it has been labeled as safe to test, the CI workflows
will start executing and we'll be able to make sure everything is working as expected.

Let us know if you need any help!

github-actions · 2026-05-25T04:36:42Z

Hi there 👋 Thanks for your contribution!

The OpenMetadata team will review the PR shortly! Once it has been labeled as safe to test, the CI workflows
will start executing and we'll be able to make sure everything is working as expected.

Let us know if you need any help!

gitar-bot · 2026-05-25T04:37:11Z

Code Review ✅ Approved 2 resolved / 2 findings

Limits search_metadata response size with a 100k character cap and 0.8 safety factor to prevent LLM context overflow. Resolves excessive log noise by downgrading response size messaging to DEBUG.

✅ 2 resolved

✅ Performance: INFO-level log on every search response is noisy

📄 openmetadata-mcp/src/main/java/org/openmetadata/mcp/tools/SearchMetadataTool.java:345-348
Line 345-348 logs the response size at INFO level for every search_metadata invocation. In a production environment with frequent MCP calls, this will generate significant log volume. Consider using DEBUG level for the per-request size logging and keeping only the WARN for the trimming case (which is already at WARN).

✅ Edge Case: Proportional trimming may not bring response under the cap

📄 openmetadata-mcp/src/main/java/org/openmetadata/mcp/tools/SearchMetadataTool.java:350-354
The trimming logic assumes results are uniformly sized (targetCount = size * MAX / serialized.length()). If early results are significantly larger than average (e.g., entities with long descriptions or many tags), the trimmed response may still exceed MAX_RESPONSE_CHARS. Consider either re-serializing after trim to verify, or applying a small safety factor (e.g., multiply the denominator by 1.2).

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Pull request overview

This PR mitigates LLM context-window overflows caused by overly large search_metadata responses in the MCP module by adding a hard response-size cap and updating the tool schema guidance to encourage smaller result sets for broad queries.

Changes:

Added a MAX_RESPONSE_CHARS cap (100k) to search_metadata responses and trim results when exceeded.
Updated the tool schema (tools.json) to guide smaller size values for broad/generic queries and adjusted the pagination example default.
Refined the “many results” guidance message to push toward narrower queries.

Reviewed changes

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

File	Description
`openmetadata-mcp/src/main/java/org/openmetadata/mcp/tools/SearchMetadataTool.java`	Adds response-size measurement + trimming logic and updates user guidance messaging.
`openmetadata-mcp/src/main/resources/json/data/mcp/tools.json`	Updates the `size` parameter description and example to reduce broad-query payload sizes.

github-actions · 2026-05-25T09:00:17Z

Hi there 👋 Thanks for your contribution!

The OpenMetadata team will review the PR shortly! Once it has been labeled as safe to test, the CI workflows
will start executing and we'll be able to make sure everything is working as expected.

Let us know if you need any help!

github-actions · 2026-05-25T09:01:18Z

Hi there 👋 Thanks for your contribution!

The OpenMetadata team will review the PR shortly! Once it has been labeled as safe to test, the CI workflows
will start executing and we'll be able to make sure everything is working as expected.

Let us know if you need any help!

github-actions · 2026-05-25T09:11:03Z

Hi there 👋 Thanks for your contribution!

The OpenMetadata team will review the PR shortly! Once it has been labeled as safe to test, the CI workflows
will start executing and we'll be able to make sure everything is working as expected.

Let us know if you need any help!

github-actions · 2026-05-26T05:27:32Z

Hi there 👋 Thanks for your contribution!

The OpenMetadata team will review the PR shortly! Once it has been labeled as safe to test, the CI workflows
will start executing and we'll be able to make sure everything is working as expected.

Let us know if you need any help!

github-actions · 2026-05-26T05:29:18Z

Hi there 👋 Thanks for your contribution!

The OpenMetadata team will review the PR shortly! Once it has been labeled as safe to test, the CI workflows
will start executing and we'll be able to make sure everything is working as expected.

Let us know if you need any help!

github-actions · 2026-05-26T08:06:13Z

🟡 Playwright Results — all passed (10 flaky)

✅ 4247 passed · ❌ 0 failed · 🟡 10 flaky · ⏭️ 87 skipped

Shard	Passed	Flaky	Skipped
✅ Shard 1	299	0	4
✅ Shard 2	805	0	8
🟡 Shard 3	792	4	8
🟡 Shard 4	844	1	12
🟡 Shard 5	718	1	47
🟡 Shard 6	789	4	8

🟡 10 flaky test(s) (passed on retry)

Features/KnowledgeCenterTextEditor.spec.ts › Rich Text Editor - Text Formatting (shard 3, 1 retry)
Features/KnowledgeCenterTextEditor.spec.ts › Rich Text Editor - Text Formatting (shard 3, 1 retry)
Features/Table.spec.ts › Table pagination with sorting should works (shard 3, 1 retry)
Flow/ExploreAggregationCountsMatching.spec.ts › should verify left panel counts and tab search results for normal search (shard 3, 2 retries)
Pages/CustomProperties.spec.ts › Set & Update all CP types on apiCollection (shard 4, 1 retry)
Pages/ExplorePageRightPanel_KnowledgeCenter.spec.ts › Should remove user owner for knowledgeCenter (shard 5, 1 retry)
Pages/Lineage/LineageFilters.spec.ts › Verify lineage schema filter selection (shard 6, 1 retry)
Pages/Lineage/LineageRightPanel.spec.ts › Verify custom properties tab IS visible for supported type: searchIndex (shard 6, 1 retry)
Pages/Lineage/PlatformLineage.spec.ts › Verify domain platform view (shard 6, 1 retry)
Pages/ServiceEntity.spec.ts › Inactive Announcement create & delete (shard 6, 1 retry)

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npx playwright show-trace path/to/trace.zip    # view trace

…erflow (#28383) * fix(mcp): cap search_metadata response size and truncate columnNames * fix(mcp): remove column truncation, guide LLM to use smaller page sizes

…erflow (#28383) * fix(mcp): cap search_metadata response size and truncate columnNames * fix(mcp): remove column truncation, guide LLM to use smaller page sizes (cherry picked from commit f18943d)

…erflow (#28383) * fix(mcp): cap search_metadata response size and truncate columnNames * fix(mcp): remove column truncation, guide LLM to use smaller page sizes (cherry picked from commit f18943d) (cherry picked from commit 6a627c7)

Shreyansh100704 added 2 commits May 22, 2026 21:29

fix(mcp): cap search_metadata response size and truncate columnNames

ecdc18d

fix(mcp): remove column truncation, guide LLM to use smaller page sizes

9e395b5

Shreyansh100704 requested review from Copilot and removed request for Copilot May 22, 2026 16:51

Copilot started reviewing on behalf of Shreyansh100704 May 22, 2026 16:51 View session

Merge branch 'main' into fix/mcp-result-truncation

f4370af

Shreyansh100704 enabled auto-merge (squash) May 22, 2026 16:52

gitar-bot Bot reviewed May 22, 2026

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Comment thread openmetadata-mcp/src/main/java/org/openmetadata/mcp/tools/SearchMetadataTool.java Outdated

gitar-bot Bot reviewed May 22, 2026

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Comment thread openmetadata-mcp/src/main/java/org/openmetadata/mcp/tools/SearchMetadataTool.java

fix(mcp): downgrade size log to DEBUG, add 0.8 safety factor for trim…

20addb1

…ming

Shreyansh100704 requested review from Copilot and removed request for Copilot May 22, 2026 17:08

Copilot started reviewing on behalf of Shreyansh100704 May 22, 2026 17:09 View session

Merge branch 'main' into fix/mcp-result-truncation

eea4be8

Copilot AI review requested due to automatic review settings May 25, 2026 04:36

Copilot started reviewing on behalf of Shreyansh100704 May 25, 2026 04:36 View session

Copilot AI reviewed May 25, 2026

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fix(mcp): set hasMore on size-cap trim, fix tools.json wording

cd1ba74

Shreyansh100704 requested review from Copilot and removed request for Copilot May 25, 2026 09:00

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gitar-bot Bot reviewed May 25, 2026

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Comment thread openmetadata-mcp/src/main/java/org/openmetadata/mcp/tools/SearchMetadataTool.java Outdated

test(mcp): add response-size unit tests

41f37a6

Copilot AI review requested due to automatic review settings May 25, 2026 09:10

Shreyansh100704 force-pushed the fix/mcp-result-truncation branch from 8ac97a1 to 41f37a6 Compare May 25, 2026 09:10

Shreyansh100704 removed the request for review from Copilot May 25, 2026 09:10

Copilot started reviewing on behalf of Shreyansh100704 May 25, 2026 09:10 View session

Merge branch 'main' into fix/mcp-result-truncation

ab11dc7

Copilot AI review requested due to automatic review settings May 26, 2026 05:27

Copilot started reviewing on behalf of Shreyansh100704 May 26, 2026 05:27 View session

Shreyansh100704 removed the request for review from Copilot May 26, 2026 05:27

Merge branch 'main' into fix/mcp-result-truncation

376074f

Copilot AI review requested due to automatic review settings May 26, 2026 05:28

Copilot started reviewing on behalf of Shreyansh100704 May 26, 2026 05:29 View session

Shreyansh100704 removed the request for review from Copilot May 26, 2026 05:29

pmbrull approved these changes May 26, 2026

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pmbrull added the safe to test Add this label to run secure Github workflows on PRs label May 26, 2026

pmbrull temporarily deployed to test May 26, 2026 05:45 — with GitHub Actions Inactive

Shreyansh100704 merged commit f18943d into main May 26, 2026
58 of 64 checks passed

Shreyansh100704 deleted the fix/mcp-result-truncation branch May 26, 2026 08:06

Vishnuujain mentioned this pull request Jun 9, 2026

Backport today's MCP/search/audit fixes to 1.13 #28872

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Describe your changes:

Type of change:

High-level design:

Tests:

Use cases covered

Unit tests

Backend integration tests

Ingestion integration tests

Playwright (UI) tests

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Checklist:

Summary by Gitar

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🟡 Playwright Results — all passed (10 flaky)

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Shreyansh100704 commented May 22, 2026 •

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