Clarify symlink behavior for repository file writes

Author: theinfosecguy

README.md

@@ -1288,7 +1288,7 @@ The following sets of tools are available:
   - `content`: Content of the file, exactly as it should appear once written. Do not base64-encode it; this server does that before calling the REST API. (string, required)
   - `message`: Commit message (string, required)
   - `owner`: Repository owner (username or organization) (string, required)
-  - `path`: Path where to create/update the file (string, required)
+  - `path`: Exact Git path to write. Writing to a symbolic link path rewrites the symbolic link's target path; use the linked file's path to update its contents. (string, required)
   - `repo`: Repository name (string, required)
   - `sha`: The blob SHA of the file being replaced. Required if the file already exists. (string, optional)
 

pkg/github/__toolsnaps__/create_or_update_file.snap

@@ -24,7 +24,7 @@
         "type": "string"
       },
       "path": {
-        "description": "Path where to create/update the file",
+        "description": "Exact Git path to write. Writing to a symbolic link path rewrites the symbolic link's target path; use the linked file's path to update its contents.",
         "type": "string"
       },
       "repo": {

pkg/github/__toolsnaps__/push_files.snap

@@ -21,7 +21,7 @@
               "type": "string"
             },
             "path": {
-              "description": "path to the file",
+              "description": "Exact Git path to write. Writing to a symbolic link path replaces the link with a regular file; use the linked file's path to update its contents.",
               "type": "string"
             }
           },

pkg/github/repositories.go

@@ -433,7 +433,7 @@ SHA MUST be provided for existing file updates.
 					},
 					"path": {
 						Type:        "string",
-						Description: "Path where to create/update the file",
+						Description: "Exact Git path to write. Writing to a symbolic link path rewrites the symbolic link's target path; use the linked file's path to update its contents.",
 					},
 					"content": {
 						Type:        "string",
@@ -1575,7 +1575,7 @@ func PushFiles(t translations.TranslationHelperFunc) inventory.ServerTool {
 							Properties: map[string]*jsonschema.Schema{
 								"path": {
 									Type:        "string",
-									Description: "path to the file",
+									Description: "Exact Git path to write. Writing to a symbolic link path replaces the link with a regular file; use the linked file's path to update its contents.",
 								},
 								"content": {
 									Type:        "string",

pkg/github/tools.go

@@ -38,10 +38,11 @@ var (
 		InstructionsFunc: generateContextToolsetInstructions,
 	}
 	ToolsetMetadataRepos = inventory.ToolsetMetadata{
-		ID:          "repos",
-		Description: "GitHub Repository related tools",
-		Default:     true,
-		Icon:        "repo",
+		ID:               "repos",
+		Description:      "GitHub Repository related tools",
+		Default:          true,
+		Icon:             "repo",
+		InstructionsFunc: generateReposToolsetInstructions,
 	}
 	ToolsetMetadataGit = inventory.ToolsetMetadata{
 		ID:          "git",

pkg/github/toolset_instructions.go

@@ -9,6 +9,12 @@ func generateContextToolsetInstructions(_ *inventory.Inventory) string {
 	return "Always call 'get_me' first to understand current user permissions and context."
 }
 
+func generateReposToolsetInstructions(_ *inventory.Inventory) string {
+	return `## Repository file writes
+
+'get_file_contents' may return the target contents when a path is a symbolic link, but repository file writes use exact Git paths and do not follow symbolic links. To edit content that a symlink points to, write to the target path.`
+}
+
 func generateIssuesToolsetInstructions(_ *inventory.Inventory) string {
 	return `## Issues
 

pkg/github/toolset_instructions_test.go

@@ -0,0 +1,86 @@
+package github
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/github/github-mcp-server/pkg/inventory"
+	"github.com/github/github-mcp-server/pkg/translations"
+	"github.com/google/jsonschema-go/jsonschema"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRepositoryInstructionsExplainSymlinkWriteSemantics(t *testing.T) {
+	t.Setenv("DISABLE_INSTRUCTIONS", "false")
+
+	reposInventory, err := inventory.NewBuilder().
+		SetTools([]inventory.ServerTool{{Toolset: ToolsetMetadataRepos}}).
+		WithToolsets([]string{"repos"}).
+		WithServerInstructions().
+		Build()
+	require.NoError(t, err)
+
+	instructions := strings.ToLower(reposInventory.Instructions())
+	assert.Contains(t, instructions, "## repository file writes")
+	assert.Contains(t, instructions, "may return the target contents")
+	assert.Contains(t, instructions, "do not follow symbolic links")
+
+	defaultInventory, err := inventory.NewBuilder().
+		SetTools([]inventory.ServerTool{
+			{Toolset: ToolsetMetadataContext},
+			{Toolset: ToolsetMetadataRepos},
+		}).
+		WithToolsets([]string{"default"}).
+		WithServerInstructions().
+		Build()
+	require.NoError(t, err)
+	assert.Contains(t, strings.ToLower(defaultInventory.Instructions()), "## repository file writes")
+
+	contextInventory, err := inventory.NewBuilder().
+		SetTools([]inventory.ServerTool{{Toolset: ToolsetMetadataContext}}).
+		WithToolsets([]string{"context"}).
+		WithServerInstructions().
+		Build()
+	require.NoError(t, err)
+	assert.NotContains(t, strings.ToLower(contextInventory.Instructions()), "## repository file writes")
+}
+
+func TestFileWritePathsExplainSymlinkWriteSemantics(t *testing.T) {
+	createSchema, ok := CreateOrUpdateFile(translations.NullTranslationHelper).Tool.InputSchema.(*jsonschema.Schema)
+	require.True(t, ok)
+	pushSchema, ok := PushFiles(translations.NullTranslationHelper).Tool.InputSchema.(*jsonschema.Schema)
+	require.True(t, ok)
+	createPath := createSchema.Properties["path"]
+	require.NotNil(t, createPath)
+	pushFiles := pushSchema.Properties["files"]
+	require.NotNil(t, pushFiles)
+	require.NotNil(t, pushFiles.Items)
+	pushPath := pushFiles.Items.Properties["path"]
+	require.NotNil(t, pushPath)
+
+	tools := []struct {
+		name             string
+		description      string
+		expectedBehavior string
+	}{
+		{
+			name:             "create_or_update_file",
+			description:      createPath.Description,
+			expectedBehavior: "rewrites the symbolic link's target path",
+		},
+		{
+			name:             "push_files",
+			description:      pushPath.Description,
+			expectedBehavior: "replaces the link with a regular file",
+		},
+	}
+
+	for _, tool := range tools {
+		t.Run(tool.name, func(t *testing.T) {
+			description := strings.ToLower(tool.description)
+			assert.Contains(t, description, "exact git path")
+			assert.Contains(t, description, tool.expectedBehavior)
+		})
+	}
+}