[MCP] describe_entities tool fixes and refactoring

[souvikghosh04]

Why make this change?

Closes on

• [Enh]: Add DML tool: describe_entities #2827

Added fixes and refactored the describe_entities tool to support entity metadata discovery for AI agents and LLM clients before performing CRUD operations.

What is this change?

• Expose entity descriptions with proper null handling
• Expose field description for entities of type stored-procedure with parameter metadata
• Expose permissions for all entities with distinct values
• Added nameOnly parameter to return lightweight response (entity names and descriptions only)
• Added entities parameter to filter results by specific entity names
• Implemented proper error handling using McpResponseBuilder pattern
• Added support for relationships, mappings, and primary key information
• Improved response structure with metadata section including mode and count

How was this tested?

Functional testing using Insomnia client by running DAB in localhost and local SQL DB database

• MCP endpoint: http://localhost:5000/mcp
• JSON payload (details below)
• Validating the response

Expected (In-progress) format of entity description in response-

{
  "entities": [
    {
      "name": "entity-name",
      "description": "entity description",
      "type": "Table",
      "fields": [
        {
          "name": "field-name",
          "type": "unknown",
          "description": "field description"
        }
      ],
      "permissions": [
        "CREATE",
        "READ",
        "UPDATE",
        "DELETE"
      ],
      "primaryKey": ["id"],
      "relationships": [...],
      "mappings": {...}
    }
  ],
  "count": 1,
  "mode": "full"
}

Sample Request(s)

POST http://localhost:5000/mcp

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

POST http://localhost:5000/mcp

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "describe_entities",
    "arguments": {
      "nameOnly": true
    }
  },
  "id": 2
}

POST http://localhost:5000/mcp

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "describe_entities",
    "arguments": {
      "entities": ["Book", "Publisher"]
    }
  },
  "id": 1
}

[Copilot]

Pull Request Overview

This PR renames the describe-entities tool to describe_entities and enhances its functionality to provide comprehensive entity metadata including descriptions, fields for stored procedures, and permissions.

• Renamed tool from describe-entities to describe_entities across configuration and implementation
• Enhanced entity response to include descriptions, fields for stored procedures, and permissions
• Added proper documentation and error handling to the tool implementation

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/Config/ObjectModel/DmlToolsConfig.cs	Updated comments to reflect the new tool name
src/Config/Converters/DmlToolsConfigConverter.cs	Updated JSON property name and validation logic
src/Cli/ConfigGenerator.cs	Updated logging message to use new tool name
src/Cli/Commands/ConfigureOptions.cs	Updated CLI option name for the tool
src/Azure.DataApiBuilder.Mcp/BuiltInTools/DescribeEntitiesTool.cs	Major refactoring with enhanced functionality and documentation
schemas/dab.draft.schema.json	Updated JSON schema property name and description

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[anushakolan]

LGTM. I will test this with Claude to see if there are any other errors.

[souvikghosh04]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 6 pipeline(s).

[RubenCerna2079]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 6 pipeline(s).

[RubenCerna2079]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 6 pipeline(s).

[RubenCerna2079]

LGTM!

The changes have been made