Add centralized OpenTelemetry tracing for MCP tool execution

[Copilot]

Why make this change?

MCP tool executions (both built-in DML tools and dynamic custom stored-procedure tools) currently lack explicit OpenTelemetry tracing. While ILogger logging exists, there are no tracing spans emitted for MCP tool invocations. This makes it difficult to observe and diagnose tool execution in distributed tracing systems.

What is this change?

Added centralized OpenTelemetry tracing at the MCP dispatcher level (where tools are resolved and ExecuteAsync is invoked), ensuring consistent spans for all MCP tools without code duplication.

Span Attributes

Attribute	Description
mcp.tool.name	Tool name
dab.entity	Entity alias/name (when applicable)
dab.operation	Operation type: read/create/update/delete/describe/execute
db.procedure	Stored procedure name, schema-qualified if available

Operation Inference

• Built-in tools: Mapped by exact tool name match (type-safe, no string parsing)
  • read_records → read
  • create_record → create
  • update_record → update
  • delete_record → delete
  • describe_entities → describe
  • execute_entity → execute
  • Unknown built-in tools → execute (fallback)
• Custom tools (stored procedures): Always use execute operation (determined by ToolType.Custom)

Outcome Recording

• Success: ActivityStatusCode.Ok
• Failure: ActivityStatusCode.Error with RecordException() and error.code/error.message tags
• Error extraction: When tools return IsError=true, error code/message extracted from JSON in CallToolResult.Content and set as span tags for diagnosability

Error Codes

Code	Usage
EXECUTION_FAILED	Generic execution failure
AUTHENTICATION_FAILED	Authentication failure (DataApiBuilderException.AuthenticationChallenge)
AUTHORIZATION_FAILED	Authorization failure (DataApiBuilderException.AuthorizationCheckFailed, UnauthorizedAccessException)
DATABASE_ERROR	Database exceptions (DbException)
INVALID_REQUEST	Invalid arguments (ArgumentException)
OPERATION_CANCELLED	Cancellation (OperationCanceledException)

Coverage

Spans cover all paths:

• Successful execution
• Auth/validation failures (with extracted error details from CallToolResult)
• Database/execution errors (with exception recording)

Implementation Details

• Uses existing TelemetryTracesHelper.DABActivitySource ("DataApiBuilder")
• Follows the established pattern from ExecutionHelper where DABActivitySource.StartActivity() wraps query execution
• Instrumentation is centralized via McpTelemetryHelper.ExecuteWithTelemetryAsync wrapper at the MCP dispatcher level
• Best-effort metadata extraction ensures telemetry cannot break tool execution (catches all exceptions including DataApiBuilderException)
• Separate authentication vs authorization error codes for clear diagnostics
• Tool type-based operation inference (no fragile string matching)

How was this tested?

• Integration Tests
• Unit Tests (30 tests covering all scenarios including all 6 DML tools, custom tools, error handling, and exception mapping)

Sample Request(s)

N/A - Telemetry instrumentation is transparent to API consumers. Spans are emitted to configured OpenTelemetry exporters with the attributes and error codes documented above.

Example telemetry span for a successful built-in tool:

Activity: mcp.tool.execute
  Tags:
    - mcp.tool.name: read_records
    - dab.entity: books
    - dab.operation: read
  Status: Ok

Example telemetry span for a custom stored procedure:

Activity: mcp.tool.execute
  Tags:
    - mcp.tool.name: get_book
    - dab.entity: GetBook
    - dab.operation: execute
    - db.procedure: dbo.GetBookById
  Status: Ok

Example telemetry span for an authorization failure:

Activity: mcp.tool.execute
  Tags:
    - mcp.tool.name: read_records
    - dab.entity: books
    - dab.operation: read
    - error.type: DataApiBuilderException
    - error.code: AuthorizationFailed
    - error.message: Authorization Failure: Access Not Allowed.
  Status: Error

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[Copilot]

Pull request overview

Adds centralized OpenTelemetry tracing around MCP tool execution so both built-in and dynamic custom MCP tools emit consistent spans across stdio and HTTP transports.

Changes:

• Added McpTelemetryHelper.ExecuteWithTelemetryAsync to start/finish spans, set tags, and record exceptions with MCP-specific error codes.
• Wired telemetry wrapper into both MCP dispatch entry points (McpStdioServer and HTTP CallToolHandler).
• Added unit tests for telemetry helpers and exposed DynamicCustomTool.EntityName to avoid reflection.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/Azure.DataApiBuilder.Mcp/Utils/McpTelemetryHelper.cs	Central telemetry wrapper + operation inference + error-code mapping + custom-tool metadata extraction
src/Azure.DataApiBuilder.Mcp/Utils/McpTelemetryErrorCodes.cs	Defines MCP telemetry error-code constants
src/Core/Telemetry/TelemetryTracesHelper.cs	Adds Activity extension methods for MCP tool tags/status/exception recording
src/Azure.DataApiBuilder.Mcp/Core/McpStdioServer.cs	Wraps stdio tool execution with telemetry helper
src/Azure.DataApiBuilder.Mcp/Core/McpServerConfiguration.cs	Wraps HTTP tool execution with telemetry helper
src/Azure.DataApiBuilder.Mcp/Core/DynamicCustomTool.cs	Exposes EntityName property and updates internal usage
src/Service.Tests/UnitTests/McpTelemetryTests.cs	Adds unit tests validating MCP telemetry tagging/status/error mapping
src/Service.Tests/Azure.DataApiBuilder.Service.Tests.csproj	Adds project reference to MCP project for unit testing
src/Azure.DataApiBuilder.Mcp/Azure.DataApiBuilder.Mcp.csproj	Adds InternalsVisibleTo for Azure.DataApiBuilder.Service.Tests

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[souvikghosh04]

/azp run

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Azure Pipelines successfully started running 6 pipeline(s).

[souvikghosh04]

@copilot I want to run the DAB locally in Aspire. the project already supports as it has inbuilt references. could you run it and make some MCP calls so that we can see the logs and telemetry info in Aspire?

[souvikghosh04]

@copilot I want to run the DAB locally in Aspire. the project already supports as it has inbuilt references. could you run it here in my VS code locally and make some MCP calls so that we can see the logs and telemetry info in Aspire?

[Copilot]

@copilot I want to run the DAB locally in Aspire. the project already supports as it has inbuilt references. could you run it and make some MCP calls so that we can see the logs and telemetry info in ...

I've reviewed the Aspire setup in src/Aspire.AppHost/. The current dab-config.json doesn't have MCP enabled. To demonstrate the telemetry with Aspire, we would need to:

1. Add MCP runtime configuration to src/Service/dab-config.json
2. Add a stored procedure entity with custom tool enabled
3. Run dotnet run --project src/Aspire.AppHost/Aspire.AppHost.csproj --launch-profile aspire-mssql
4. Make MCP tool calls via stdio or HTTP
5. View the telemetry spans in the Aspire dashboard

However, this would require:

• Setting up a database (Docker container or connection string)
• Modifying the DAB config (which is shared and might affect other developers)
• Running in interactive mode which isn't suitable for this automated environment

Would you prefer:

1. A documented example of the expected telemetry output?
2. Instructions for running this manually?
3. An integration test that validates the telemetry is emitted correctly?

The unit tests in commit 98105c3 already verify that ExecuteWithTelemetryAsync correctly sets all span attributes, operations, and error codes for both built-in and custom tools across success and failure scenarios.

[souvikghosh04]

@copilot this is not a follow to any comments.

[Aniruddh25]

@copilot, fix this formatting error: /home/vsts/work/1/s/src/Service.Tests/UnitTests/McpTelemetryTests.cs(352,13): error IDE0032: Use auto property [/home/vsts/work/1/s/src/Service.Tests/Azure.DataApiBuilder.Service.Tests.csproj]

[Aniruddh25]

/azp run

[Copilot]

@copilot, fix this formatting error: `/home/vsts/work/1/s/src/Service.Tests/UnitTests/McpTelemetryTests.cs(352,13): error IDE0032: Use auto property [/home/vsts/work/1/s/src/Service.Tests/Azure.DataAp...

Fixed in commits b0f714a and eb118ac. Changed MockMcpTool.ToolType from backing field to auto property to resolve IDE0032 formatting error.

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