feat: add ability to create atlas search indexes MCP-275 #692

nirinchev · 2025-10-27T15:11:45Z

Proposed changes

This adds support for creating atlas search indexes. Dropping and listing is already supported, so needed no changes.

Notable omissions from the schema, that we will want to evaluate based on user feedback and internal testing:

analyzers - based on consultation with the Search team
mappings.dynamic.typeSet - preview feature
searchAnalyzer - based on consultation with the Search team
storedSource - based on testing of model performance
synonyms - for simplicity
typeSets - for simplicity
mappings.fields.* - the fields definition only includes the type and uses passthrough for the remaining fields. We'll have to evaluate its performance and if necessary, define the complete json schema.

Copilot

Pull Request Overview

This PR adds support for creating Atlas Search (lexical) indexes through the MCP server. The changes enable users to create Atlas Search indexes with both dynamic and explicit field mappings, complementing the existing support for listing and dropping search indexes.

Key changes:

Added Atlas Search index creation support to create-index tool with comprehensive schema validation
Enhanced testing to differentiate between search and vector search indexes
Added accuracy tests for various Atlas Search index creation scenarios

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
`src/tools/mongodb/create/createIndex.ts`	Adds `atlasSearchIndexDefinition` schema and implements search index creation logic
`tests/integration/tools/mongodb/create/createIndex.test.ts`	Adds comprehensive integration tests for Atlas Search index creation scenarios
`tests/integration/tools/mongodb/delete/dropIndex.test.ts`	Refactors tests to handle both search and vector search indexes separately
`tests/accuracy/createIndex.test.ts`	Adds accuracy test cases for Atlas Search index creation with various configurations
`tests/accuracy/sdk/accuracyTestingClient.ts`	Removes deprecated `--connectionString` flag from CLI arguments
`README.md`	Updates documentation to remove deprecated `--connectionString` flag

Comments suppressed due to low confidence (1)

tests/integration/tools/mongodb/create/createIndex.test.ts:1

The index names are being evaluated at test definition time rather than test execution time. If getSearchIndexName() and getVectorIndexName() depend on beforeEach setup, these calls will execute before the setup runs, potentially returning undefined or stale values. Wrap these in functions: { description: "search", indexName: () => getSearchIndexName() } and update the test to call the function.

import { describeWithMongoDB, validateAutoConnectBehavior, waitUntilSearchIsReady } from "../mongodbHelpers.js";

src/tools/mongodb/create/createIndex.ts

tests/integration/tools/mongodb/delete/dropIndex.test.ts

coveralls · 2025-10-27T16:15:44Z

Pull Request Test Coverage Report for Build 19331710057

Details

165 of 168 (98.21%) changed or added relevant lines in 3 files are covered.
No unchanged relevant lines lost coverage.
Overall coverage increased (+0.2%) to 80.397%

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/tools/args.ts	9	12	75.0%

Totals
Change from base Build 19331702101:	0.2%
Covered Lines:	6581
Relevant Lines:	8073

💛 - Coveralls

nirinchev · 2025-10-28T10:39:42Z

src/tools/mongodb/create/createIndex.ts

 import { quantizationEnum, similarityEnum } from "../../../common/search/vectorSearchEmbeddingsManager.js";

 export class CreateIndexTool extends MongoDBToolBase {
-    private vectorSearchIndexDefinition = z.object({


This is best viewed with the "Hide whitespace" option - it's just prettier reformatting the indents.

nirinchev · 2025-10-28T10:45:51Z

tests/accuracy/sdk/accuracyTestingClient.ts

        });

-        const args = [MCP_SERVER_CLI_SCRIPT, "--connectionString", mdbConnectionString, ...additionalArgs];
+        const args = [MCP_SERVER_CLI_SCRIPT, mdbConnectionString, ...additionalArgs];


--connectionString is deprecated so using the positional argument.

src/tools/mongodb/create/createIndex.ts

kmruiz · 2025-10-30T12:59:14Z

src/tools/mongodb/create/createIndex.ts

+    private atlasSearchIndexDefinition = z
+        .object({
+            type: z.literal("search"),
+            analyzer: z


Probably this should be an enum of the analyzers.

Discussing with the search team, searchAnalyzer and analyzers is not something we need to support based on current usage patterns. We can add support in the future if we see customer demand for it.

kmruiz · 2025-10-30T13:01:25Z

src/tools/mongodb/create/createIndex.ts

+                    "The analyzer to use for the index. Can be one of the built-in lucene analyzers (`lucene.standard`, `lucene.simple`, `lucene.whitespace`, `lucene.keyword`), a language-specific analyzer, such as `lucene.cjk` or `lucene.czech`, or a custom analyzer defined in the Atlas UI."
+                ),
+            mappings: z
+                .object({


Lack support of:

numPartitions

searchAnalyzer vs analyze

custom analyzers

storedSources

synonyms

typeSets

https://www.mongodb.com/docs/atlas/atlas-search/index-definitions/?deployment-type=atlas&interface=driver&language=nodejs#std-label-ref-index-definitions

We could say that custom analyzers are not that important, but storedSources is actually relevant most of the times.

The args shape is based on the POC the search team did for index support and I was going off of the assumption that they've selected the fields that they see the most value in exposing to LLMs. I realize there's a lot more configuration that's possible, I'm just not sure how much of that is stuff we expect agents to configure vs an actual human who wants to fine-tune the index.

A POC to see the feasibility to create search indexes and production code are likely to have different requirements.

typeSets is still in preview, so I'm leaving it out for now.

numPartitions was added

searchAnalyzer and analyzers are out of scope per search team's recommendation

I'm leaving the following out of this PR for now as they have more complex schema and have been more error prone when testing:

synonyms

storedSources

We can add them as we move toward GA and build out a more comprehensive testing suite.

src/tools/mongodb/create/createIndex.ts

kmruiz

The current implementation lacks support for multiple important fields, and it should be discussed if we want to support them or not.

kmruiz · 2025-10-30T13:34:15Z

src/tools/mongodb/create/createIndex.ts

+                            z.string().describe("The field name"),
+                            z
+                                .object({
+                                    type: z


Objects will require additional fields depending on the type. I know passthrough will keep them, but we should document them so the agent knows which ones to use and how. For example, autocomplete supports defining a custom analyzer, how to tokenize (which is really important) and similarity functions.

The exact shape is extremely complex to represent in a json schema. I'm worried that being overly specific will result in this being more harmful than helpful, especially if we expect the majority of the use cases to revolve around just specifying the type.

Yep, the schema is complicated, it has a lot of options that are not compatible even between them. We should have proper documentation of which ones we want to expose and which ones not, something that we haven't discussed yet because supporting the most used bits of Atlas Search is already a substantial effort.

Leaving this out of scope for now and we can decide how much detail to provide as we build out a more comprehensive testing suite.

nirinchev requested a review from a team as a code owner October 27, 2025 15:11

nirinchev requested a review from Copilot October 27, 2025 16:03

Base automatically changed from ni/feature-flags to main October 27, 2025 16:03

nirinchev added 2 commits October 27, 2025 17:04

add support for creating atlas search indexes

b63916e

add more tests

3fab3b7

nirinchev force-pushed the ni/atlas-search branch from e9cef48 to 3fab3b7 Compare October 27, 2025 16:04

Copilot AI reviewed Oct 27, 2025

View reviewed changes

src/tools/mongodb/create/createIndex.ts Show resolved Hide resolved

src/tools/mongodb/create/createIndex.ts Show resolved Hide resolved

tests/integration/tools/mongodb/delete/dropIndex.test.ts Show resolved Hide resolved

tweak descriptions and errors

809aa9a

nirinchev commented Oct 28, 2025

View reviewed changes

gagik approved these changes Oct 28, 2025

View reviewed changes

nirinchev changed the title ~~feat: add ability to create atlas search indexes~~ feat: add ability to create atlas search indexes MCP-275 Oct 28, 2025

replace arg as a function

23d1a17

kmruiz reviewed Oct 30, 2025

View reviewed changes

src/tools/mongodb/create/createIndex.ts Show resolved Hide resolved

kmruiz reviewed Oct 30, 2025

View reviewed changes

src/tools/mongodb/create/createIndex.ts Show resolved Hide resolved

kmruiz requested changes Oct 30, 2025

View reviewed changes

kmruiz reviewed Oct 30, 2025

View reviewed changes

nirinchev added 8 commits November 11, 2025 10:27

Merge branch 'main' into ni/atlas-search

3c88363

add numPartitions

5221d92

fix: don't extract fields from lexical search indexes

b08f5b1

clean up type definitions

6dc2dd8

Merge branch 'main' into ni/assert-atlas-search

d6d55a8

Merge branch 'ni/assert-atlas-search' into ni/atlas-search

8aa1980

fix agg test

a4ccfae

Merge branch 'main' into ni/atlas-search

b9c0479

feat: add ability to create atlas search indexes MCP-275 #692

Are you sure you want to change the base?

feat: add ability to create atlas search indexes MCP-275 #692

Uh oh!

Conversation

nirinchev commented Oct 27, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Proposed changes

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull Request Overview

Reviewed Changes

Uh oh!

Uh oh!

Uh oh!

Uh oh!

coveralls commented Oct 27, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Pull Request Test Coverage Report for Build 19331710057

Details

💛 - Coveralls

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

kmruiz left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

nirinchev commented Oct 27, 2025 •

edited

Loading

coveralls commented Oct 27, 2025 •

edited

Loading