[MCP] Prevent duplicating entities between custom tools and describe_entities #3076

souvikghosh04 · 2026-01-22T08:13:03Z

Why make this change?

Closes on - MCP-CustomTool: describe_entities filtering #3043

With custom tools, stored procedure entities could get listed in describe_entities even when they are configured as custom-tool-only (with dml-tools: false). This creates duplication since they already appear in tools/list. We need to filter stored procedures with dml-tools: false from describe_entities to avoid this duplication.

What is this change?

Added filtering logic to exclude stored procedure entities when dml-tools is explicitly set to false
The filtering ensures stored procedures are removed from describe_entities only when they are custom-tool-only (not available for DML operations)
Stored procedures with dml-tools: true (or null/default) continue to appear in describe_entities even if they have custom-tool: true, allowing dual exposure when needed

How was this tested?

Unit Tests
Manual Tests

Sample Request(s)

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "describe_entities"
  },
  "id": 1
}

…_entities

Copilot

Pull request overview

This PR prevents stored-procedure entities that are already exposed as dedicated custom MCP tools from being duplicated in the describe_entities response.

Changes:

Added filtering in DescribeEntitiesTool to skip stored procedures with entity.Mcp.CustomToolEnabled == true.
Added new MSTest coverage validating stored procedure filtering and ensuring tables/views remain unaffected.

Reviewed changes

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

File	Description
src/Azure.DataApiBuilder.Mcp/BuiltInTools/DescribeEntitiesTool.cs	Filters out custom-tool-enabled stored procedures from `describe_entities` results.
src/Service.Tests/Mcp/DescribeEntitiesFilteringTests.cs	Adds tests verifying filtering behavior across stored procedures, tables/views, and `nameOnly` mode.

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src/Service.Tests/Mcp/DescribeEntitiesFilteringTests.cs

src/Azure.DataApiBuilder.Mcp/BuiltInTools/DescribeEntitiesTool.cs

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

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src/Service.Tests/Mcp/DescribeEntitiesFilteringTests.cs

src/Azure.DataApiBuilder.Mcp/BuiltInTools/DescribeEntitiesTool.cs

src/Service.Tests/Mcp/DescribeEntitiesFilteringTests.cs

souvikghosh04 · 2026-01-22T09:49:02Z

/azp run

azure-pipelines · 2026-01-22T09:49:29Z

Azure Pipelines successfully started running 6 pipeline(s).

JerryNixon · 2026-01-22T17:42:33Z

Desired logic

	DML TOOLS = TRUE	DML TOOLS = FALSE
CUSTOM TOOL = TRUE	✔ describe_entities ✔ tools/list	✘ describe_entities ✔ tools/list
CUSTOM TOOL = FALSE	✔ describe_entities ✘ tools/list	✘ describe_entities ✘ tools/list

RubenCerna2079 · 2026-01-29T02:32:34Z

src/Azure.DataApiBuilder.Mcp/BuiltInTools/DescribeEntitiesTool.cs

                    }
+                    // All entities were filtered because they're custom-tool-only - only return this specific error
+                    // if ALL configured entities were filtered (not just some). This prevents misleading errors
+                    // when entities fail to build for other reasons (e.g., exceptions in Build*EntityInfo).


nit:

Suggested change

// when entities fail to build for other reasons (e.g., exceptions in Build*EntityInfo).

// when entities fail to build for other reasons (e.g., exceptions in Build*EntityInfo functions).

RubenCerna2079 · 2026-01-29T02:35:10Z

src/Azure.DataApiBuilder.Mcp/BuiltInTools/DescribeEntitiesTool.cs

+                    // All entities were filtered because they're custom-tool-only - only return this specific error
+                    // if ALL configured entities were filtered (not just some). This prevents misleading errors
+                    // when entities fail to build for other reasons (e.g., exceptions in Build*EntityInfo).
+                    else if (filteredCustomToolCount > 0 &&


Wouldn't we also want a situation where only some of the entities were filtered?

Just saw its purpose is to show the user when all their tools are custom-tools, although it might be a good idea to also give the user the information that their SPs that are custom-tools are in a different place.

Aniruddh25 · 2026-01-29T05:53:26Z

src/Azure.DataApiBuilder.Mcp/BuiltInTools/DescribeEntitiesTool.cs

+                        // - custom-tool: true, dml-tools: false → Filtered (appears only in tools/list)
+                        // - custom-tool: false, dml-tools: false → Filtered (entity fully disabled for MCP)
+                        // When dml-tools is true (or default), the entity appears in describe_entities.
+                        if (entity.Source.Type == EntitySourceType.StoredProcedure &&


For other types of entities (that are not stored procedures), when dmltool enabled is false, do we still need them to be shown in describe_entities?

Or is the dmltoolenabled flag only specific to entities that are stored procs?

If the dmltoolenabled/Mcp section under entity is non-null only when it is a stored procedure entity, we should not need to check for the type of entity to be stored procedure.

Aniruddh25 · 2026-01-29T06:03:21Z

src/Service.Tests/Mcp/DescribeEntitiesFilteringTests.cs

+        public async Task DescribeEntities_TablesAndViewsUnaffectedByFiltering()
+        {
+            // Arrange
+            RuntimeConfig config = CreateConfigWithMixedEntityTypes();


what if some of the tables/views also have dml_tools : false? Shouldnt we filter those out too?

Aniruddh25

Waiting on what needs to be done for non stored proc entities

[MCP] Prevent duplicating tool list between custom tools and describe…

0a4c986

…_entities

souvikghosh04 requested a review from Copilot January 22, 2026 08:14

Copilot started reviewing on behalf of souvikghosh04 January 22, 2026 08:14 View session

souvikghosh04 self-assigned this Jan 22, 2026

souvikghosh04 added mssql an issue thats specific to mssql mcp-server labels Jan 22, 2026

souvikghosh04 added this to Data API builder Jan 22, 2026

github-project-automation bot moved this to Todo in Data API builder Jan 22, 2026

souvikghosh04 added this to the Jan 2026 milestone Jan 22, 2026

souvikghosh04 linked an issue Jan 22, 2026 that may be closed by this pull request

MCP-CustomTool: describe_entities filtering #3043

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souvikghosh04 moved this from Todo to In Progress in Data API builder Jan 22, 2026

Copilot AI reviewed Jan 22, 2026

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src/Azure.DataApiBuilder.Mcp/BuiltInTools/DescribeEntitiesTool.cs Outdated Show resolved Hide resolved

Minor fixes and refactoring

e701a87

souvikghosh04 requested a review from Copilot January 22, 2026 08:45

Copilot started reviewing on behalf of souvikghosh04 January 22, 2026 08:46 View session

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souvikghosh04 added 2 commits January 22, 2026 14:26

Copilot review fixes

c793712

Copilot review fixes

b9fd106

souvikghosh04 marked this pull request as ready for review January 22, 2026 10:46

souvikghosh04 requested review from Alekhya-Polavarapu, Aniruddh25, RubenCerna2079, aaronburtle, anushakolan, neeraj-sharma2592, rusamant, sourabh1007 and vadeveka as code owners January 22, 2026 10:46

JerryNixon added the do-not-merge label Jan 22, 2026

Fix behavior of dmltools and custom tools combinations

e2cc3e8

souvikghosh04 removed the do-not-merge label Jan 22, 2026

souvikghosh04 changed the title ~~[MCP] Prevent duplicating tool list between custom tools and describe~~ [MCP] Prevent duplicating entities between custom tools and describe_entities Jan 23, 2026

RubenCerna2079 self-assigned this Jan 28, 2026

RubenCerna2079 reviewed Jan 29, 2026

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Aniruddh25 reviewed Jan 29, 2026

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Aniruddh25 requested changes Jan 29, 2026

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github-project-automation bot moved this from In Progress to Review In Progress in Data API builder Jan 29, 2026

	// when entities fail to build for other reasons (e.g., exceptions in Build*EntityInfo).
	// when entities fail to build for other reasons (e.g., exceptions in Build*EntityInfo functions).

[MCP] Prevent duplicating entities between custom tools and describe_entities #3076

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[MCP] Prevent duplicating entities between custom tools and describe_entities #3076

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souvikghosh04 commented Jan 22, 2026

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JerryNixon commented Jan 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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souvikghosh04 commented Jan 22, 2026 •

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