Generate server instructions in Inventory (#1869)

* carry over from #1863

* remove unused inv

* update toolsnap

---------

Co-authored-by: Sam Morrow <info@sam-morrow.com>

Author: tommaso-moro

internal/ghmcp/server.go

@@ -171,16 +171,31 @@ func NewMCPServer(cfg MCPServerConfig) (*mcp.Server, error) {
 
 	enabledToolsets := resolveEnabledToolsets(cfg)
 
-	// For instruction generation, we need actual toolset names (not nil).
-	// nil means "use defaults" in inventory, so expand it for instructions.
-	instructionToolsets := enabledToolsets
-	if instructionToolsets == nil {
-		instructionToolsets = github.GetDefaultToolsetIDs()
+	// Create feature checker
+	featureChecker := createFeatureChecker(cfg.EnabledFeatures)
+
+	// Build and register the tool/resource/prompt inventory
+	inventoryBuilder := github.NewInventory(cfg.Translator).
+		WithDeprecatedAliases(github.DeprecatedToolAliases).
+		WithReadOnly(cfg.ReadOnly).
+		WithToolsets(enabledToolsets).
+		WithTools(cfg.EnabledTools).
+		WithFeatureChecker(featureChecker).
+		WithServerInstructions()
+
+	// Apply token scope filtering if scopes are known (for PAT filtering)
+	if cfg.TokenScopes != nil {
+		inventoryBuilder = inventoryBuilder.WithFilter(github.CreateToolScopeFilter(cfg.TokenScopes))
+	}
+
+	inventory, err := inventoryBuilder.Build()
+	if err != nil {
+		return nil, fmt.Errorf("failed to build inventory: %w", err)
 	}
 
 	// Create the MCP server
 	serverOpts := &mcp.ServerOptions{
-		Instructions: github.GenerateInstructions(instructionToolsets),
+		Instructions: inventory.Instructions(),
 		Logger:       cfg.Logger,
 		CompletionHandler: github.CompletionsHandler(func(_ context.Context) (*gogithub.Client, error) {
 			return clients.rest, nil
@@ -203,9 +218,6 @@ func NewMCPServer(cfg MCPServerConfig) (*mcp.Server, error) {
 	ghServer.AddReceivingMiddleware(addGitHubAPIErrorToContext)
 	ghServer.AddReceivingMiddleware(addUserAgentsMiddleware(cfg, clients.rest, clients.gqlHTTP))
 
-	// Create feature checker
-	featureChecker := createFeatureChecker(cfg.EnabledFeatures)
-
 	// Create dependencies for tool handlers
 	deps := github.NewBaseDeps(
 		clients.rest,
@@ -228,24 +240,6 @@ func NewMCPServer(cfg MCPServerConfig) (*mcp.Server, error) {
 		}
 	})
 
-	// Build and register the tool/resource/prompt inventory
-	inventoryBuilder := github.NewInventory(cfg.Translator).
-		WithDeprecatedAliases(github.DeprecatedToolAliases).
-		WithReadOnly(cfg.ReadOnly).
-		WithToolsets(enabledToolsets).
-		WithTools(cfg.EnabledTools).
-		WithFeatureChecker(featureChecker)
-
-	// Apply token scope filtering if scopes are known (for PAT filtering)
-	if cfg.TokenScopes != nil {
-		inventoryBuilder = inventoryBuilder.WithFilter(github.CreateToolScopeFilter(cfg.TokenScopes))
-	}
-
-	inventory, err := inventoryBuilder.Build()
-	if err != nil {
-		return nil, fmt.Errorf("failed to build inventory: %w", err)
-	}
-
 	if unrecognized := inventory.UnrecognizedToolsets(); len(unrecognized) > 0 {
 		fmt.Fprintf(os.Stderr, "Warning: unrecognized toolsets ignored: %s\n", strings.Join(unrecognized, ", "))
 	}

pkg/github/instructions_test.go

@@ -28,10 +28,11 @@ var (
 		Icon:        "check-circle",
 	}
 	ToolsetMetadataContext = inventory.ToolsetMetadata{
-		ID:          "context",
-		Description: "Tools that provide context about the current user and GitHub context you are operating in",
-		Default:     true,
-		Icon:        "person",
+		ID:               "context",
+		Description:      "Tools that provide context about the current user and GitHub context you are operating in",
+		Default:          true,
+		Icon:             "person",
+		InstructionsFunc: generateContextToolsetInstructions,
 	}
 	ToolsetMetadataRepos = inventory.ToolsetMetadata{
 		ID:          "repos",
@@ -45,16 +46,18 @@ var (
 		Icon:        "git-branch",
 	}
 	ToolsetMetadataIssues = inventory.ToolsetMetadata{
-		ID:          "issues",
-		Description: "GitHub Issues related tools",
-		Default:     true,
-		Icon:        "issue-opened",
+		ID:               "issues",
+		Description:      "GitHub Issues related tools",
+		Default:          true,
+		Icon:             "issue-opened",
+		InstructionsFunc: generateIssuesToolsetInstructions,
 	}
 	ToolsetMetadataPullRequests = inventory.ToolsetMetadata{
-		ID:          "pull_requests",
-		Description: "GitHub Pull Request related tools",
-		Default:     true,
-		Icon:        "git-pull-request",
+		ID:               "pull_requests",
+		Description:      "GitHub Pull Request related tools",
+		Default:          true,
+		Icon:             "git-pull-request",
+		InstructionsFunc: generatePullRequestsToolsetInstructions,
 	}
 	ToolsetMetadataUsers = inventory.ToolsetMetadata{
 		ID:          "users",
@@ -93,9 +96,10 @@ var (
 		Icon:        "bell",
 	}
 	ToolsetMetadataDiscussions = inventory.ToolsetMetadata{
-		ID:          "discussions",
-		Description: "GitHub Discussions related tools",
-		Icon:        "comment-discussion",
+		ID:               "discussions",
+		Description:      "GitHub Discussions related tools",
+		Icon:             "comment-discussion",
+		InstructionsFunc: generateDiscussionsToolsetInstructions,
 	}
 	ToolsetMetadataGists = inventory.ToolsetMetadata{
 		ID:          "gists",
@@ -108,9 +112,10 @@ var (
 		Icon:        "shield",
 	}
 	ToolsetMetadataProjects = inventory.ToolsetMetadata{
-		ID:          "projects",
-		Description: "GitHub Projects related tools",
-		Icon:        "project",
+		ID:               "projects",
+		Description:      "GitHub Projects related tools",
+		Icon:             "project",
+		InstructionsFunc: generateProjectsToolsetInstructions,
 	}
 	ToolsetMetadataStargazers = inventory.ToolsetMetadata{
 		ID:          "stargazers",