Add reaction tools for issues and pull requests by timrogers · Pull Request #2732 · github/github-mcp-server

timrogers · 2026-06-19T16:06:06Z

Summary

Add reaction support for issues, issue comments, and pull request review comments while keeping standalone reaction tools behind the granular tool feature flags.

Default users can add reactions through existing comment tools to avoid adding more default tools:

add_issue_comment can add an issue/PR comment, add a reaction to an issue/PR, add a reaction to an issue/PR timeline comment, or combine a comment with a reaction.
add_reply_to_pull_request_comment can reply to a pull request review comment, add a reaction to a pull request review comment, or do both.

Granular users also get standalone tools:

add_issue_reaction
add_issue_comment_reaction
add_pull_request_review_comment_reaction

Why

Reactions are a fundamental part of GitHub's interaction model. Clients should be able to add reactions programmatically just as they can create issues, comments, and reviews, without increasing the default tool surface more than necessary.

What changed

Added granular standalone reaction tools for issues, issue comments, and PR review comments.
Extended default comment tools with optional reaction parameters.
Clarified numeric comment ID requirements, especially for PR review comments where callers must use the numeric #discussion_r... ID rather than a GraphQL review thread node ID.
Added validation so reaction/comment combinations are explicit and do not silently ignore comment IDs.
Ordered combined reaction+comment operations so the idempotent reaction happens before creating the non-idempotent comment/reply, reducing duplicate-comment risk on retries.
Updated tests, toolsnaps, and generated docs.

MCP impact

New tool added
- Three standalone reaction tools are added to granular issue and pull request toolsets.
Existing tool changed
- add_issue_comment and add_reply_to_pull_request_comment now support reactions.

Prompts tested (tool changes only)

"Add a reaction to issue 42 in my-repo"
"Add a reaction to the issue comment I just made"
"Add a reaction to the PR review comment feedback"
"Reply to this PR review comment and add a rocket reaction"

Security / limits

No security or limits impact
- Reactions follow existing GitHub API permissions and use the same client authentication/error handling as other write tools.

Tool renaming

I am not renaming existing MCP tools as part of this PR

Lint & tests

Linted locally with ./script/lint
Tested locally with ./script/test

Docs

Updated (README / docs / examples)
- README.md and generated docs updated via script/generate-docs.
- Toolsnaps updated in pkg/github/__toolsnaps__/.

Closes #2757

Copilot

Pull request overview

This PR adds three new MCP write tools that let clients create emoji reactions on GitHub issues, issue comments, and pull request review comments, extending the server’s “write” surface area to cover a core GitHub interaction.

Changes:

Added three new tools: add_issue_reaction, add_issue_comment_reaction, and add_pull_request_review_comment_reaction.
Wired the tools into the global tool inventory and added handler tests with mocked HTTP endpoints.
Updated generated documentation and added new tool schema snapshots (__toolsnaps__).

Show a summary per file

File	Description
README.md	Documents the three new tools and their parameters in the generated tool listing.
pkg/github/tools.go	Registers the three new tools in `AllTools` so they’re available to clients.
pkg/github/issues_granular.go	Implements `add_issue_reaction` and `add_issue_comment_reaction` tool schemas and handlers.
pkg/github/pullrequests_granular.go	Implements `add_pull_request_review_comment_reaction` tool schema and handler.
pkg/github/helper_test.go	Adds mocked endpoint patterns for the reactions REST endpoints.
pkg/github/granular_tools_test.go	Adds toolsnap coverage and handler tests for the new reaction tools.
pkg/github/toolsnaps/add_issue_reaction.snap	New snapshot for `add_issue_reaction` tool schema.
pkg/github/toolsnaps/add_issue_comment_reaction.snap	New snapshot for `add_issue_comment_reaction` tool schema.
pkg/github/toolsnaps/add_pull_request_review_comment_reaction.snap	New snapshot for `add_pull_request_review_comment_reaction` tool schema.

Copilot's findings

Files reviewed: 9/9 changed files
Comments generated: 3

Implement three granular-only tools for adding emoji reactions: - add_issue_reaction: Add reaction to an issue - add_issue_comment_reaction: Add reaction to an issue comment - add_pull_request_review_comment_reaction: Add reaction to a PR review comment All tools are feature-flagged with FeatureFlagEnable set to enable them only when clients request granular toolsets. Tools use go-github's Reactions service and return minimal ID response on success (HTTP 201). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Remove feature flag gates from reaction tools so they're available to all clients regardless of granular toolset preference. Reaction tools are naturally atomic operations and work equally well in both modes. Updates test expectations to exclude reaction tools from granular-only test assertions, since they're now always available. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

A-Georgiou

Looks good to me 🚀

timrogers · 2026-06-19T17:20:03Z

Tested manually locally and this is all working. We could consider adding tools to remove reactions, but I think this is a good incremental step and we can choose to add more later.

Return reaction URLs in minimal responses and clarify issue tools apply to pull requests where applicable. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

phillipschandler19-web

internal/ghmcp/server_test.go.github/actions/build-ui/action.ymlREADME.mdhttps://github.com/modelcontextprotocol/modelcontextprotocol/issues/1489

Keep the standalone reaction tools behind granular feature flags to avoid expanding the default tool count. Add optional reaction support to the existing issue comment and pull request comment reply tools, requiring at least one of body or reaction. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Document that PR review comment reaction inputs require the numeric review comment ID, not the GraphQL review thread node ID returned by review thread APIs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add optional comment_id support so the default add_issue_comment tool can react to a specific issue or pull request comment without exposing a separate default reaction tool. Keep body creation tied to issue_number and require reaction targets to provide either issue_number or comment_id. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 16/16 changed files
Comments generated: 4

 		{
 			name: "comment creation fails",
 			mockedClient: MockHTTPClientWithHandlers(map[string]http.HandlerFunc{
 				PostReposIssuesCommentsByOwnerByRepoByIssueNumber: http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 					w.WriteHeader(http.StatusUnprocessableEntity)
 					_, _ = w.Write([]byte(`{"message": "Invalid request"}`))
 				}),
 			}),
 			requestArgs: map[string]any{
 				"owner":        "owner",
 				"repo":         "repo",
 				"issue_number": float64(42),
-				"body":         "",
+				"body":         "This is a test comment",
 			},
 			expectError:    false,
-			expectedErrMsg: "missing required parameter: body",
+			expectedErrMsg: "failed to create comment",
 		},


+				createdComment, resp, err := client.Issues.CreateComment(ctx, owner, repo, issueNumber, comment)
 				if err != nil {
-					return utils.NewToolResultErrorFromErr("failed to read response body", err), nil, nil
+					return utils.NewToolResultErrorFromErr("failed to create comment", err), nil, nil
+				}


+			if hasReaction && !hasIssueNumber && !hasCommentID {
+				return utils.NewToolResultError("issue_number or comment_id is required when reaction is provided"), nil, nil
+			}


 		ListIssueFields(t),
 		IssueWrite(t),
 		AddIssueComment(t),
+		AddIssueReaction(t),
+		AddIssueCommentReaction(t),


Apply reactions before creating comments or replies so retrying a failed combined call cannot duplicate the non-idempotent comment operation. Also reject issue comment IDs without a reaction target to avoid silently ignoring the field. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 16/16 changed files
Comments generated: 6

+			if hasBody && !hasIssueNumber {
+				return utils.NewToolResultError("issue_number is required when body is provided"), nil, nil
+			}
+			if hasReaction && !hasIssueNumber && !hasCommentID {
+				return utils.NewToolResultError("issue_number or comment_id is required when reaction is provided"), nil, nil
+			}
+			if hasCommentID && !hasReaction {
+				return utils.NewToolResultError("comment_id can only be provided when reaction is provided"), nil, nil
+			}


+// AddIssueReaction adds a reaction to an issue or pull request.
+func AddIssueReaction(t translations.TranslationHelperFunc) inventory.ServerTool {
+	st := NewTool(


+// AddPullRequestReviewCommentReaction adds a reaction to a pull request review comment.
+func AddPullRequestReviewCommentReaction(t translations.TranslationHelperFunc) inventory.ServerTool {
+	st := NewTool(


Keep standalone reaction tool registrations next to the granular issue and pull request tools they belong with, so the default compound tool sections stay focused. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 16/16 changed files
Comments generated: 4

Rename the standalone reaction tool constructors to match the granular tool naming convention and clarify issue comment reaction IDs for pull request comments. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Comments suppressed due to low confidence (1)

pkg/github/issues_test.go:631

In this test, the failure case sets expectedErrMsg but the assertion path does not verify the tool call actually returned an error result (result.IsError). This can allow regressions where the tool returns a non-error result containing the substring. Align the failure handling with the rest of the suite by asserting result.IsError and reading the error via getErrorResult().

			expectedErrMsg: "failed to create comment",
		},
	}

	for _, tc := range tests {

Files reviewed: 16/16 changed files
Comments generated: 0 new

timrogers requested a review from a team as a code owner June 19, 2026 16:06

Copilot AI review requested due to automatic review settings June 19, 2026 16:06

Copilot started reviewing on behalf of timrogers June 19, 2026 16:06 View session

Copilot AI reviewed Jun 19, 2026

View reviewed changes

Comment thread pkg/github/issues_granular.go

Comment thread pkg/github/issues_granular.go Outdated

Comment thread pkg/github/pullrequests_granular.go Outdated

timrogers and others added 4 commits June 19, 2026 17:25

Update toolsnaps with aligned reaction tool descriptions

774b75b

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Align reaction tool descriptions with codebase style

94c6f2c

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

timrogers force-pushed the timrogers/planning-reaction-tools branch from 44c2a5e to 94c6f2c Compare June 19, 2026 16:26

A-Georgiou previously approved these changes Jun 19, 2026

View reviewed changes

Improve reaction tool responses and wording

30da9da

Return reaction URLs in minimal responses and clarify issue tools apply to pull requests where applicable. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

timrogers dismissed A-Georgiou’s stale review via 30da9da June 19, 2026 17:28

A-Georgiou previously approved these changes Jun 19, 2026

View reviewed changes

phillipschandler19-web reviewed Jun 20, 2026

View reviewed changes

SamMorrowDrums dismissed A-Georgiou’s stale review via 009bb7b June 23, 2026 12:29

This was referenced Jun 23, 2026

Track: reaction tools for issues and pull requests (#2732) #2757

Open

Track: reaction tools for issues and pull requests (#2732) #2758

Closed

Clarify PR review comment IDs for reactions

e6276cf

Document that PR review comment reaction inputs require the numeric review comment ID, not the GraphQL review thread node ID returned by review thread APIs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

SamMorrowDrums mentioned this pull request Jun 23, 2026

Track: reaction tools for issues and pull requests (#2732) #2759

Open

4 tasks

SamMorrowDrums requested a review from Copilot June 23, 2026 13:37

Merge branch 'main' into timrogers/planning-reaction-tools

9908fbf

Copilot started reviewing on behalf of SamMorrowDrums June 23, 2026 13:38 View session

Copilot AI reviewed Jun 23, 2026

View reviewed changes

SamMorrowDrums requested a review from Copilot June 23, 2026 19:32

Copilot started reviewing on behalf of SamMorrowDrums June 23, 2026 19:33 View session

Copilot AI reviewed Jun 23, 2026

View reviewed changes

Group reaction tools with granular registrations

d218ebe

Keep standalone reaction tool registrations next to the granular issue and pull request tools they belong with, so the default compound tool sections stay focused. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

SamMorrowDrums requested a review from Copilot June 23, 2026 19:38

Copilot started reviewing on behalf of SamMorrowDrums June 23, 2026 19:39 View session

Copilot AI reviewed Jun 23, 2026

View reviewed changes

Comment thread pkg/github/issues_granular.go

Comment thread pkg/github/pullrequests_granular.go

Comment thread pkg/github/issues.go

Comment thread pkg/github/pullrequests.go

Align granular reaction tool constructors

7fff6f2

Rename the standalone reaction tool constructors to match the granular tool naming convention and clarify issue comment reaction IDs for pull request comments. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

SamMorrowDrums requested a review from Copilot June 23, 2026 19:45

Copilot started reviewing on behalf of SamMorrowDrums June 23, 2026 19:45 View session

Copilot AI reviewed Jun 23, 2026

View reviewed changes

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Summary

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timrogers commented Jun 19, 2026 •

edited by SamMorrowDrums

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