feat: gate get_file_blame behind file_blame feature flag

The git blame tool adds a new tool to the inventory, which carries a
context-footprint cost for every client. Gate it behind a new
file_blame feature flag (user opt-in via --features / X-MCP-Features)
that is also auto-enabled in insiders mode, so it is not advertised by
default.

Regenerated README, feature-flags.md and insiders-features.md docs.

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

Author: SamMorrowDrums

README.md

@@ -1229,17 +1229,6 @@ The following sets of tools are available:
   - `repo`: Repository name (string, required)
   - `sha`: Commit SHA, branch name, or tag name (string, required)
 
-- **get_file_blame** - Get file blame information
-  - **Required OAuth Scopes**: `repo`
-  - `after`: Cursor for pagination. Use the cursor from the previous response. (string, optional)
-  - `end_line`: Optional 1-based ending line of the window of interest. Must be >= start_line when both are provided. (number, optional)
-  - `owner`: Repository owner (username or organization) (string, required)
-  - `path`: Path to the file in the repository, relative to the repository root (string, required)
-  - `perPage`: Results per page for pagination (min 1, max 100) (number, optional)
-  - `ref`: Git reference (branch, tag, or commit SHA). Defaults to the repository's default branch (HEAD). (string, optional)
-  - `repo`: Repository name (string, required)
-  - `start_line`: Optional 1-based starting line of the window of interest. Only ranges overlapping [start_line, end_line] are returned, clamped to the window. (number, optional)
-
 - **get_file_contents** - Get file or directory contents
   - **Required OAuth Scopes**: `repo`
   - `owner`: Repository owner (username or organization) (string, required)

docs/feature-flags.md

@@ -287,4 +287,17 @@ runtime behavior (such as output formatting) won't appear here.
   - `repo`: Repository name (string, required)
   - `title`: The new title for the pull request (string, required)
 
+### `file_blame`
+
+- **get_file_blame** - Get file blame information
+  - **Required OAuth Scopes**: `repo`
+  - `after`: Cursor for pagination. Use the cursor from the previous response. (string, optional)
+  - `end_line`: Optional 1-based ending line of the window of interest. Must be >= start_line when both are provided. (number, optional)
+  - `owner`: Repository owner (username or organization) (string, required)
+  - `path`: Path to the file in the repository, relative to the repository root (string, required)
+  - `perPage`: Results per page for pagination (min 1, max 100) (number, optional)
+  - `ref`: Git reference (branch, tag, or commit SHA). Defaults to the repository's default branch (HEAD). (string, optional)
+  - `repo`: Repository name (string, required)
+  - `start_line`: Optional 1-based starting line of the window of interest. Only ranges overlapping [start_line, end_line] are returned, clamped to the window. (number, optional)
+
 <!-- END AUTOMATED FEATURE FLAG TOOLS -->

docs/insiders-features.md

@@ -107,6 +107,19 @@ The list below is generated from the Go source. It covers tool **inventory and s
   - `since`: Filter by date (ISO 8601 timestamp) (string, optional)
   - `state`: Filter by state, by default both open and closed issues are returned when not provided (string, optional)
 
+### `file_blame`
+
+- **get_file_blame** - Get file blame information
+  - **Required OAuth Scopes**: `repo`
+  - `after`: Cursor for pagination. Use the cursor from the previous response. (string, optional)
+  - `end_line`: Optional 1-based ending line of the window of interest. Must be >= start_line when both are provided. (number, optional)
+  - `owner`: Repository owner (username or organization) (string, required)
+  - `path`: Path to the file in the repository, relative to the repository root (string, required)
+  - `perPage`: Results per page for pagination (min 1, max 100) (number, optional)
+  - `ref`: Git reference (branch, tag, or commit SHA). Defaults to the repository's default branch (HEAD). (string, optional)
+  - `repo`: Repository name (string, required)
+  - `start_line`: Optional 1-based starting line of the window of interest. Only ranges overlapping [start_line, end_line] are returned, clamped to the window. (number, optional)
+
 <!-- END AUTOMATED INSIDERS TOOLS -->
 
 ---

pkg/github/feature_flags.go

@@ -16,6 +16,11 @@ const FeatureFlagIFCLabels = "ifc_labels"
 // and field_values enrichment in list_issues / search_issues output.
 const FeatureFlagIssueFields = "remote_mcp_issue_fields"
 
+// FeatureFlagFileBlame is the feature flag name for the get_file_blame tool,
+// which exposes git blame information for a file. It is gated so the extra tool
+// is not advertised by default, keeping the tool surface small unless opted in.
+const FeatureFlagFileBlame = "file_blame"
+
 // AllowedFeatureFlags is the allowlist of feature flags that can be enabled
 // by users via --features CLI flag or X-MCP-Features HTTP header.
 // Only flags in this list are accepted; unknown flags are silently ignored.
@@ -27,6 +32,7 @@ var AllowedFeatureFlags = []string{
 	FeatureFlagIssueFields,
 	FeatureFlagIssuesGranular,
 	FeatureFlagPullRequestsGranular,
+	FeatureFlagFileBlame,
 }
 
 // InsidersFeatureFlags is the list of feature flags that insiders mode enables.
@@ -37,6 +43,7 @@ var InsidersFeatureFlags = []string{
 	MCPAppsFeatureFlag,
 	FeatureFlagCSVOutput,
 	FeatureFlagIssueFields,
+	FeatureFlagFileBlame,
 }
 
 // FeatureFlags defines runtime feature toggles that adjust tool behavior.

pkg/github/repositories.go

@@ -2384,7 +2384,7 @@ func validateBlamePath(p string) error {
 }
 
 func GetFileBlame(t translations.TranslationHelperFunc) inventory.ServerTool {
-	return NewTool(
+	st := NewTool(
 		ToolsetMetadataRepos,
 		mcp.Tool{
 			Name: "get_file_blame",
@@ -2679,6 +2679,8 @@ func GetFileBlame(t translations.TranslationHelperFunc) inventory.ServerTool {
 			return utils.NewToolResultText(string(payload)), nil, nil
 		},
 	)
+	st.FeatureFlagEnable = FeatureFlagFileBlame
+	return st
 }
 
 // ListRepositoryCollaborators creates a tool to list collaborators of a GitHub repository.

pkg/github/repositories_test.go

@@ -4712,6 +4712,10 @@ func Test_GetFileBlame(t *testing.T) {
 	tool := serverTool.Tool
 	require.NoError(t, toolsnaps.Test(tool.Name, tool))
 
+	// get_file_blame is gated so it is not advertised unless the feature flag
+	// (or insiders mode) opts it in.
+	assert.Equal(t, FeatureFlagFileBlame, serverTool.FeatureFlagEnable, "get_file_blame must be gated behind the file_blame feature flag")
+
 	schema, ok := tool.InputSchema.(*jsonschema.Schema)
 	require.True(t, ok, "InputSchema should be *jsonschema.Schema")
 	assert.Equal(t, "get_file_blame", tool.Name)