[MCP] Centralize JSON‑RPC error handling, standardize MCP response envelope, and add default anonymous role for stdio mode. #3035
+84
−41
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Contributor
Author
|
/azp run |
|
Azure Pipelines successfully started running 6 pipeline(s). |
anushakolan
requested review from
Alekhya-Polavarapu,
Aniruddh25,
RubenCerna2079,
aaronburtle,
neeraj-sharma2592,
rusamant,
sourabh1007,
souvikghosh04 and
vadeveka
as code owners
anushakolan
changed the title
mcp-stdio mode code changes.
Contributor
There was a problem hiding this comment.
Pull request overview
This PR is a follow-up to #2983 that improves the MCP stdio server implementation by centralizing JSON-RPC error handling, standardizing response writing, and adding an implicit default role when none is provided.
- Centralized all JSON-RPC error codes into a single
JsonRpcErrorCodesclass - Standardized response handling through shared
WriteResultandWriteErrorhelper methods - Added implicit default role of "anonymous" when
--mcp-stdiois used without a role parameter
Reviewed changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| src/Service/Utilities/McpStdioHelper.cs | Added [NotNullWhen(true)] attribute to enforce non-null role guarantee, implemented implicit default role of "anonymous", and removed unnecessary service scope creation since services are singletons |
| src/Service/Program.cs | Added copyright header (formatting artifact in diff) |
| src/Azure.DataApiBuilder.Mcp/Core/JsonRpcErrorCodes.cs | New file defining centralized JSON-RPC 2.0 error codes for consistent error handling across the MCP server |
| src/Azure.DataApiBuilder.Mcp/Core/McpStdioServer.cs | Replaced hardcoded error codes with constants from JsonRpcErrorCodes, refactored initialize handler to use standardized WriteResult, and updated server name in initialization response |
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
Aniruddh25
approved these changes
Dec 30, 2025
Collaborator
Aniruddh25
left a comment
Aniruddh25
left a comment
There was a problem hiding this comment.
Approved, but please fix the title to mention "what" the code changes are. Follow up PR doesnt convey much information unless you look into the changes. The PR titles are seen directly in the Release notes, so they should be more meaningful. For example, in this case, it is refactor to use common JsonRpcErrorCodes
Aniruddh25
reviewed
Dec 30, 2025
anushakolan
changed the title
mcp-stdio mode code changes.
anushakolan
changed the title
Contributor
Author
|
/azp run |
|
Azure Pipelines successfully started running 6 pipeline(s). |
Contributor
Author
|
/azp run |
|
Azure Pipelines successfully started running 6 pipeline(s). |
Collaborator
|
/azp run |
Aniruddh25
approved these changes
Jan 14, 2026
|
Azure Pipelines successfully started running 6 pipeline(s). |
Contributor
Author
|
/azp run |
|
Azure Pipelines successfully started running 6 pipeline(s). |
souvikghosh04
requested changes
Jan 15, 2026
Contributor
souvikghosh04
left a comment
souvikghosh04
left a comment
There was a problem hiding this comment.
Added some comments for appropriate way of naming and versioning of MCP server and some naming/structuring conventions.
Contributor
Author
|
/azp run |
|
Azure Pipelines successfully started running 6 pipeline(s). |
Contributor
Author
|
/azp run |
|
Azure Pipelines successfully started running 6 pipeline(s). |
souvikghosh04
approved these changes
Jan 16, 2026
Contributor
souvikghosh04
left a comment
souvikghosh04
left a comment
There was a problem hiding this comment.
Thanks for addressing the comments. Approved.
anushakolan
added a commit
that referenced
this pull request
Jan 16, 2026
…velope, and add default anonymous role for stdio mode. (#3035) ## Why make this change? This is a follow up PR for, #2983 to address some of the newer comments. ## What is this change? 1. Centralized JSON‑RPC error handling: all standard JSON‑RPC error codes are now defined in one place and used consistently throughout the MCP server (for things like parse errors, invalid requests, unknown methods, invalid parameters, and internal errors). 2. Standardized how responses are written: both successful results and errors now go through shared helpers, so every MCP response has a consistent JSON‑RPC envelope and is easy to change or audit. 3. Added an implicit default role to be `anonymous` when no role is provided in `mcp-stdio` mode. ## How was this tested? Tested manually by calling all the CRUD tools and execute tool. Added an MCP server in VS Code in `C:\DAB\data-api-builder\.vscode\mcp.json` `"dab-with-exe": { "command": "C:\\DAB\\data-api-builder\\out\\publish\\Debug\\net8.0\\win-x64\\dab\\Microsoft.DataApiBuilder.exe", "args": ["start", "--mcp-stdio", "--config", "C:\\DAB\\data-api-builder\\dab-config.json"], "env": { "DAB_ENVIRONMENT": "Development" } }` 1. When calling tools with `Authenticated` all tools pass. 2. When calling tools with `Anonymous`, all tools except `describe-entities` fail with permission denied error. 5. When calling tools without any role parameter, all tools except `describe-entities` fail with permission denied error. (cherry picked from commit de8f074)
anushakolan
added a commit
that referenced
this pull request
Jan 16, 2026
…velope, and add default anonymous role for stdio mode. (#3035) ## Why make this change? This is a follow up PR for, #2983 to address some of the newer comments. ## What is this change? 1. Centralized JSON‑RPC error handling: all standard JSON‑RPC error codes are now defined in one place and used consistently throughout the MCP server (for things like parse errors, invalid requests, unknown methods, invalid parameters, and internal errors). 2. Standardized how responses are written: both successful results and errors now go through shared helpers, so every MCP response has a consistent JSON‑RPC envelope and is easy to change or audit. 3. Added an implicit default role to be `anonymous` when no role is provided in `mcp-stdio` mode. ## How was this tested? Tested manually by calling all the CRUD tools and execute tool. Added an MCP server in VS Code in `C:\DAB\data-api-builder\.vscode\mcp.json` `"dab-with-exe": { "command": "C:\\DAB\\data-api-builder\\out\\publish\\Debug\\net8.0\\win-x64\\dab\\Microsoft.DataApiBuilder.exe", "args": ["start", "--mcp-stdio", "--config", "C:\\DAB\\data-api-builder\\dab-config.json"], "env": { "DAB_ENVIRONMENT": "Development" } }` 1. When calling tools with `Authenticated` all tools pass. 2. When calling tools with `Anonymous`, all tools except `describe-entities` fail with permission denied error. 5. When calling tools without any role parameter, all tools except `describe-entities` fail with permission denied error. (cherry picked from commit de8f074)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Why make this change?
This is a follow up PR for, #2983 to address some of the newer comments.
What is this change?
anonymouswhen no role is provided inmcp-stdiomode.How was this tested?
Tested manually by calling all the CRUD tools and execute tool.
Added an MCP server in VS Code in
C:\DAB\data-api-builder\.vscode\mcp.json"dab-with-exe": { "command": "C:\\DAB\\data-api-builder\\out\\publish\\Debug\\net8.0\\win-x64\\dab\\Microsoft.DataApiBuilder.exe", "args": ["start", "--mcp-stdio", "--config", "C:\\DAB\\data-api-builder\\dab-config.json"], "env": { "DAB_ENVIRONMENT": "Development" } }Authenticatedall tools pass.Anonymous, all tools exceptdescribe-entitiesfail with permission denied error.describe-entitiesfail with permission denied error.