DynamicCustomTool: DB metadata based parameter support

[souvikghosh04]

Why make this change?

• Closes Parameter behaviour in MCP tool: DynamicCustomTool #3589

DynamicCustomTool (per-entity custom MCP tools) used entityConfig.Source.Parameters / ParameterMetadata for parameter validation and defaults. This meant:

• Parameters discovered only via DB metadata (not listed in config) were rejected.
• Defaults were applied all-or-nothing instead of per-missing-parameter.

What is this change?

• Validate against DB metadata: After authorization, safe-cast dbObject to DatabaseStoredProcedure and validate user-supplied params against spDefinition.Parameters (source of truth populated by FillSchemaForStoredProcedureAsync).
• Per-param config defaults: Iterate spDefinition.Parameters; for each missing param with HasConfigDefault == true, inject ConfigDefaultValue. User-supplied params always take precedence.
• Removed old logic: Replaced entityConfig.Source.Parameters / ParameterMetadata loop.

How was this tested?

• Unit Tests

Test	Scenario
AcceptsDbDiscoveredParam	Param in DB metadata but not config - accepted
RejectsInvalidParamName (x2)	Param not in DB metadata - error
AppliesConfigDefaults	Missing params filled from HasConfigDefault/ConfigDefaultValue
UserParamsOverride	User-supplied values take precedence over config defaults
DoesNotInjectWithoutDefault	Param without HasConfigDefault is not injected
ZeroParamSP	SP with no parameters succeeds with no input

• Integration Tests

Test	Scenario
Success (x4 DataRows)	GetBook(id), InsertBook(null), InsertBook(override), GetBooks(zero-param)
GetBookById_ReturnsRecord	Validates returned data matches expected
Rejection (x2 DataRows)	Invalid param names rejected with clear error

• Manual Testing

Category	Result
Valid params / no results	Pass
Type mismatch - error	Pass
Zero-param SPs	Pass
Config defaults / partial params	Pass
Multi-param update	Pass
SQL injection (parameterized)	Pass
Boundary values (-1, 0, MAX_INT)	Pass
Empty/long/unicode strings	Pass
Read-after-write, FK errors, cross-entity	Pass

Sample Request(s)

NA

[Copilot]

Pull request overview

Note

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

Adds DB-metadata-based parameter validation and per-parameter default application for MCP stored-procedure tools, addressing scenarios where parameters are discovered only via DB metadata and defaults should apply only to missing params.

Changes:

• Validate user-supplied parameters against StoredProcedureDefinition.Parameters (DB metadata) in ExecuteEntityTool and DynamicCustomTool.
• Apply config defaults per missing parameter using ParameterDefinition.HasConfigDefault/ConfigDefaultValue.
• Add/extend unit + MSSQL integration tests and enable MCP custom tools in MSSQL config generator commands.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/Azure.DataApiBuilder.Mcp/Core/DynamicCustomTool.cs	Switches validation/defaulting to DB metadata definitions.
src/Azure.DataApiBuilder.Mcp/BuiltInTools/ExecuteEntityTool.cs	Same validation/defaulting changes for the built-in execute tool.
src/Service.Tests/Mcp/ExecuteEntityToolTests.cs	New unit tests covering validation/default application + gating.
src/Service.Tests/Mcp/ExecuteEntityToolMsSqlIntegrationTests.cs	New end-to-end MSSQL integration tests for execute tool behavior.
src/Service.Tests/Mcp/DynamicCustomToolTests.cs	Adds execution-time unit tests for DynamicCustomTool behavior.
src/Service.Tests/Mcp/DynamicCustomToolMsSqlIntegrationTests.cs	New MSSQL integration tests for DynamicCustomTool behavior.
config-generators/mssql-commands.txt	Enables --mcp.custom-tool true for stored-procedure entities used by tests.

[Aniruddh25]

Why do we have ExecuteEntityTool tests in this PR?

[souvikghosh04]

This branch was created on top of the ExecuteEntityTool fix (PR #3600) since DynamicCustomTool follows the same pattern. Because #3600 hasn't merged to main yet, GitHub shows the ExecuteEntityTool files in this diff as well.

Once #3600 merges, I'll rebase this branch onto main and those files will drop out of the diff automatically, avoiding a force-push or rewrite.

[Aniruddh25]

Approving with suggestions on fixing the tests, and few questions.

[anushakolan]

The snapshot file needs to be updated; I am approving this PR to prevent any blockers from my side.

[souvikghosh04]

waiting for #3600 to merge as this was branched out from that with related fixes.