[Agent Builder] Improve MCP tool call error message#248549
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## Summary Improves MCP tool call error messages by extracting and displaying the actual error content from the response. Per the [MCP specification](https://modelcontextprotocol.io/specification/2025-11-25/server/tools#error-handling), tool execution errors are returned as text content parts, so the error message now properly surfaces this information instead of showing an undefined response.error property. <img width="1290" height="1241" alt="CleanShot 2026-01-09 at 17 16 03" src="https://github.com/user-attachments/assets/94e0b0cb-7d4b-4bae-9266-38c65b334cfe" /> ### Checklist Check the PR satisfies following conditions. Reviewers should verify this PR satisfies this list as well. - [x] Any text added follows [EUI's writing guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses sentence case text and includes [i18n support](https://github.com/elastic/kibana/blob/main/src/platform/packages/shared/kbn-i18n/README.md) - [x] [Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html) was added for features that require explanation or tutorials - [x] [Unit or functional tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html) were updated or added to match the most common scenarios - [x] If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the [docker list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker) - [x] This was checked for breaking HTTP API changes, and any breaking changes have been approved by the breaking-change committee. The `release_note:breaking` label should be applied in these situations. - [x] [Flaky Test Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was used on any tests changed - [x] The PR description includes the appropriate Release Notes section, and the correct `release_note:*` label is applied per the [guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process) - [x] Review the [backport guidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing) and apply applicable `backport:*` labels. --------- Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>
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## Summary Improves MCP tool call error messages by extracting and displaying the actual error content from the response. Per the [MCP specification](https://modelcontextprotocol.io/specification/2025-11-25/server/tools#error-handling), tool execution errors are returned as text content parts, so the error message now properly surfaces this information instead of showing an undefined response.error property. <img width="1290" height="1241" alt="CleanShot 2026-01-09 at 17 16 03" src="https://github.com/user-attachments/assets/94e0b0cb-7d4b-4bae-9266-38c65b334cfe" /> ### Checklist Check the PR satisfies following conditions. Reviewers should verify this PR satisfies this list as well. - [x] Any text added follows [EUI's writing guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses sentence case text and includes [i18n support](https://github.com/elastic/kibana/blob/main/src/platform/packages/shared/kbn-i18n/README.md) - [x] [Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html) was added for features that require explanation or tutorials - [x] [Unit or functional tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html) were updated or added to match the most common scenarios - [x] If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the [docker list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker) - [x] This was checked for breaking HTTP API changes, and any breaking changes have been approved by the breaking-change committee. The `release_note:breaking` label should be applied in these situations. - [x] [Flaky Test Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was used on any tests changed - [x] The PR description includes the appropriate Release Notes section, and the correct `release_note:*` label is applied per the [guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process) - [x] Review the [backport guidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing) and apply applicable `backport:*` labels. --------- Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com> (cherry picked from commit 8925713)
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…249069) # Backport This will backport the following commits from `main` to `9.3`: - [[Agent Builder] Improve MCP tool call error message (#248549)](#248549) <!--- Backport version: 10.2.0 --> ### Questions ? Please refer to the [Backport tool documentation](https://github.com/sorenlouv/backport) <!--BACKPORT [{"author":{"name":"Dennis Tismenko","email":"dennis.tismenko@elastic.co"},"sourceCommit":{"committedDate":"2026-01-12T18:03:14Z","message":"[Agent Builder] Improve MCP tool call error message (#248549)\n\n## Summary\n\nImproves MCP tool call error messages by extracting and displaying the\nactual error content from the response. Per the [MCP\nspecification](https://modelcontextprotocol.io/specification/2025-11-25/server/tools#error-handling),\ntool execution errors are returned as text content parts, so the error\nmessage now properly surfaces this information instead of showing an\nundefined response.error property.\n\n\n\n<img width=\"1290\" height=\"1241\" alt=\"CleanShot 2026-01-09 at 17 16 03\"\nsrc=\"https://github.com/user-attachments/assets/94e0b0cb-7d4b-4bae-9266-38c65b334cfe\"\n/>\n\n### Checklist\n\nCheck the PR satisfies following conditions. \n\nReviewers should verify this PR satisfies this list as well.\n\n- [x] Any text added follows [EUI's writing\nguidelines](https://elastic.github.io/eui/#/guidelines/writing), uses\nsentence case text and includes [i18n\nsupport](https://github.com/elastic/kibana/blob/main/src/platform/packages/shared/kbn-i18n/README.md)\n- [x]\n[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)\nwas added for features that require explanation or tutorials\n- [x] [Unit or functional\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\nwere updated or added to match the most common scenarios\n- [x] If a plugin configuration key changed, check if it needs to be\nallowlisted in the cloud and added to the [docker\nlist](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)\n- [x] This was checked for breaking HTTP API changes, and any breaking\nchanges have been approved by the breaking-change committee. The\n`release_note:breaking` label should be applied in these situations.\n- [x] [Flaky Test\nRunner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was\nused on any tests changed\n- [x] The PR description includes the appropriate Release Notes section,\nand the correct `release_note:*` label is applied per the\n[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)\n- [x] Review the [backport\nguidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)\nand apply applicable `backport:*` labels.\n\n---------\n\nCo-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>","sha":"89257138a7985b0a1020215e6c78b913de8b3a64","branchLabelMapping":{"^v9.4.0$":"main","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["release_note:skip","backport:skip","v9.4.0"],"title":"[Agent Builder] Improve MCP tool call error message","number":248549,"url":"https://github.com/elastic/kibana/pull/248549","mergeCommit":{"message":"[Agent Builder] Improve MCP tool call error message (#248549)\n\n## Summary\n\nImproves MCP tool call error messages by extracting and displaying the\nactual error content from the response. Per the [MCP\nspecification](https://modelcontextprotocol.io/specification/2025-11-25/server/tools#error-handling),\ntool execution errors are returned as text content parts, so the error\nmessage now properly surfaces this information instead of showing an\nundefined response.error property.\n\n\n\n<img width=\"1290\" height=\"1241\" alt=\"CleanShot 2026-01-09 at 17 16 03\"\nsrc=\"https://github.com/user-attachments/assets/94e0b0cb-7d4b-4bae-9266-38c65b334cfe\"\n/>\n\n### Checklist\n\nCheck the PR satisfies following conditions. \n\nReviewers should verify this PR satisfies this list as well.\n\n- [x] Any text added follows [EUI's writing\nguidelines](https://elastic.github.io/eui/#/guidelines/writing), uses\nsentence case text and includes [i18n\nsupport](https://github.com/elastic/kibana/blob/main/src/platform/packages/shared/kbn-i18n/README.md)\n- [x]\n[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)\nwas added for features that require explanation or tutorials\n- [x] [Unit or functional\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\nwere updated or added to match the most common scenarios\n- [x] If a plugin configuration key changed, check if it needs to be\nallowlisted in the cloud and added to the [docker\nlist](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)\n- [x] This was checked for breaking HTTP API changes, and any breaking\nchanges have been approved by the breaking-change committee. The\n`release_note:breaking` label should be applied in these situations.\n- [x] [Flaky Test\nRunner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was\nused on any tests changed\n- [x] The PR description includes the appropriate Release Notes section,\nand the correct `release_note:*` label is applied per the\n[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)\n- [x] Review the [backport\nguidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)\nand apply applicable `backport:*` labels.\n\n---------\n\nCo-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>","sha":"89257138a7985b0a1020215e6c78b913de8b3a64"}},"sourceBranch":"main","suggestedTargetBranches":[],"targetPullRequestStates":[{"branch":"main","label":"v9.4.0","branchLabelMappingKey":"^v9.4.0$","isSourceBranch":true,"state":"MERGED","url":"https://github.com/elastic/kibana/pull/248549","number":248549,"mergeCommit":{"message":"[Agent Builder] Improve MCP tool call error message (#248549)\n\n## Summary\n\nImproves MCP tool call error messages by extracting and displaying the\nactual error content from the response. Per the [MCP\nspecification](https://modelcontextprotocol.io/specification/2025-11-25/server/tools#error-handling),\ntool execution errors are returned as text content parts, so the error\nmessage now properly surfaces this information instead of showing an\nundefined response.error property.\n\n\n\n<img width=\"1290\" height=\"1241\" alt=\"CleanShot 2026-01-09 at 17 16 03\"\nsrc=\"https://github.com/user-attachments/assets/94e0b0cb-7d4b-4bae-9266-38c65b334cfe\"\n/>\n\n### Checklist\n\nCheck the PR satisfies following conditions. \n\nReviewers should verify this PR satisfies this list as well.\n\n- [x] Any text added follows [EUI's writing\nguidelines](https://elastic.github.io/eui/#/guidelines/writing), uses\nsentence case text and includes [i18n\nsupport](https://github.com/elastic/kibana/blob/main/src/platform/packages/shared/kbn-i18n/README.md)\n- [x]\n[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)\nwas added for features that require explanation or tutorials\n- [x] [Unit or functional\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\nwere updated or added to match the most common scenarios\n- [x] If a plugin configuration key changed, check if it needs to be\nallowlisted in the cloud and added to the [docker\nlist](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)\n- [x] This was checked for breaking HTTP API changes, and any breaking\nchanges have been approved by the breaking-change committee. The\n`release_note:breaking` label should be applied in these situations.\n- [x] [Flaky Test\nRunner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was\nused on any tests changed\n- [x] The PR description includes the appropriate Release Notes section,\nand the correct `release_note:*` label is applied per the\n[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)\n- [x] Review the [backport\nguidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)\nand apply applicable `backport:*` labels.\n\n---------\n\nCo-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>","sha":"89257138a7985b0a1020215e6c78b913de8b3a64"}}]}] BACKPORT--> Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>
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Summary
Improves MCP tool call error messages by extracting and displaying the actual error content from the response. Per the MCP specification, tool execution errors are returned as text content parts, so the error message now properly surfaces this information instead of showing an undefined response.error property.
Checklist
Check the PR satisfies following conditions.
Reviewers should verify this PR satisfies this list as well.
release_note:breakinglabel should be applied in these situations.release_note:*label is applied per the guidelinesbackport:*labels.