Cherry pick [MCP] Added support for --mcp-stdio flag to dab start (#2983) to release 1.7
#3034
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## Why make this change?
- Add MCP stdio support to Data API Builder and wire it through both the
engine and CLI so DAB can be used as a Model Context Protocol (MCP)
server.
- Ensures MCP sessions can run under a specific DAB authorization role,
making it possible to test and use MCP tools with permissions from
`dab-config.json`.
## What is this change?
Service entrypoint
- Detects `--mcp-stdio` early, configures stdin/stdout encodings, and
redirects all non‑MCP output to STDERR to keep STDOUT clean for MCP
JSON.
- Parses an optional `role:<name>` argument (e.g. role:anonymous,
role:authenticated) and injects it into configuration as `MCP:Role`,
defaulting to `anonymous` when omitted.
- In MCP stdio mode, forces `Runtime:Host:Authentication:Provider =
"Simulator"` via in‑memory configuration so the requested role is always
available during MCP sessions.
- Starts the full ASP.NET Core host, registers all MCP tools from DI,
and runs the MCP stdio loop instead of the normal HTTP `host.Run(`).
CLI Integration
- Adds `--mcp-stdio` to `dab start` to launch the engine in MCP stdio
mode.
- Adds an optional positional `role` argument (e.g. `role:anonymous`)
captured as `StartOptions.McpRole`.
- Keeps existing behavior for non‑MCP `dab start` unchanged.
Note
- `ExecuteEntityTool` now looks for MCP tool inputs under arguments (the
standard MCP field) and falls back to the legacy parameters property
only if arguments is missing. This aligns our server with how current
MCP clients (like VS Code) actually send tool arguments, and preserves
backward compatibility for any older clients that still use parameters.
## How was this tested?
Integration-like manual testing via MCP clients against:
- Engine-based MCP server: `dotnet Azure.DataApiBuilder.Service.dll
--mcp-stdio role:authenticated`.
- CLI-based MCP server: `dab start --mcp-stdio role:authenticated`.
Manual verification of all MCP tools:
- `describe_entities` shows correct entities and effective permissions
for the active role.
- `read_records`, `create_record`, `update_record`, `delete_record`,
`execute_entity` succeed when the role has the appropriate permissions.
## Sample Request(s)
1. MCP server via CLI (dab)
`
{
"mcpServers": {
"dab-with-exe": {
"command":
"C:\\DAB\\data-api-builder\\out\\publish\\Debug\\net8.0\\win-x64\\dab\\Microsoft.DataApiBuilder.exe",
"args": ["start", "--mcp-stdio", "role:authenticated", "--config",
"C:\\DAB\\data-api-builder\\dab-config.json"],
"env": {
"DAB_ENVIRONMENT": "Development"
}
}
}
`
2. MCP server via engine DLL
`
{
"mcpServers": {
"dab": {
"command": "dotnet",
"args": [
"C:\\DAB\\data-api-builder\\out\\publish\\Debug\\net8.0\\win-x64\\dab\\Azure.DataApiBuilder.Service.dll",
"--mcp-stdio",
"role:authenticated",
"--config",
"C:\\DAB\\data-api-builder\\dab-config.json"
],
"type": "stdio"
}
}
}
`
anushakolan
requested review from
Alekhya-Polavarapu,
Aniruddh25,
RubenCerna2079,
aaronburtle,
neeraj-sharma2592,
rusamant,
sourabh1007,
souvikghosh04 and
vadeveka
as code owners
Contributor
Author
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anushakolan
changed the title
--mcp-stdio flag to dab start (#2983)[MCP] Added support for --mcp-stdio flag to dab start (#2983) to release 1.7
anushakolan
changed the title
[MCP] Added support for --mcp-stdio flag to dab start (#2983) to release 1.7[MCP] Added support for --mcp-stdio flag to dab start (#2983) to release 1.7
Contributor
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Pull request overview
This PR cherry-picks MCP (Model Context Protocol) stdio support from PR #2983 to the release 1.7 branch. It adds the --mcp-stdio flag to the dab start command, enabling Data API Builder to run as an MCP server that communicates via standard input/output using JSON-RPC protocol.
Key changes:
- Adds MCP stdio server implementation that handles JSON-RPC requests (initialize, listTools, callTool) via stdin/stdout
- Introduces
--mcp-stdioflag and optional role parameter for the CLI start command - Configures authentication to use Simulator mode when running in MCP stdio mode
Reviewed changes
Copilot reviewed 9 out of 9 changed files in this pull request and generated 12 comments.
Show a summary per file
| File | Description |
|---|---|
src/Service/Utilities/McpStdioHelper.cs |
New helper class for MCP stdio mode detection, configuration, and host execution |
src/Azure.DataApiBuilder.Mcp/IMcpStdioServer.cs |
New interface defining the MCP stdio server contract |
src/Azure.DataApiBuilder.Mcp/Core/McpStdioServer.cs |
New implementation of MCP stdio server handling JSON-RPC protocol |
src/Azure.DataApiBuilder.Mcp/Core/McpProtocolDefaults.cs |
New class defining default protocol version and configuration keys |
src/Service/Program.cs |
Updated entry point to detect MCP stdio mode, configure UTF-8 encoding, and route to appropriate host |
src/Service/Startup.cs |
Modified service configuration to force Simulator authentication in MCP stdio mode |
src/Cli/Commands/StartOptions.cs |
Added McpStdio flag and McpRole parameter to start command options |
src/Cli/ConfigGenerator.cs |
Updated to pass MCP stdio arguments to the engine when starting |
src/Cli/Exporter.cs |
Updated StartOptions instantiation to include new MCP parameters |
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Comment on lines
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| namespace Azure.DataApiBuilder.Mcp.Core | ||
| { | ||
| public interface IMcpStdioServer | ||
| { | ||
| Task RunAsync(CancellationToken cancellationToken); | ||
| } | ||
| } |
There was a problem hiding this comment.
The interface is missing necessary using directives. The Task type is used in the method signature but the System.Threading.Tasks namespace is not imported. Additionally, CancellationToken requires System.Threading namespace.
| serverInfo = new | ||
| { | ||
| name = "Data API Builder", | ||
| version = "1.0.0" |
There was a problem hiding this comment.
The hard-coded server version "1.0.0" should be replaced with the actual product version. Consider using ProductInfo.GetProductVersion() or a similar mechanism to ensure the version number reflects the actual DAB version being run.
| // Copyright (c) Microsoft Corporation. | ||
| // Licensed under the MIT License. | ||
|
|
||
| using System; |
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The copyright header comment was removed from this file. All source files in the repository should maintain consistent copyright headers for legal and attribution purposes.
Aniruddh25
requested changes
Dec 29, 2025
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Why make this change?
This change is made to cherry pick the mcp-stdio changes to the release 1.7 branch.
What is this change?
This change includes cherry picking #2983 to the release 1.7 branch.
How was this tested?
Integration-like manual testing via MCP clients against Engine-based MCP server.