Merge pull request #739 from dgageot/read-only-mcp

An agent with only read-only tools is read-only

Author: rumpl

pkg/mcp/server.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/modelcontextprotocol/go-sdk/mcp"
 
+	"github.com/docker/cagent/pkg/agent"
 	"github.com/docker/cagent/pkg/agentfile"
 	"github.com/docker/cagent/pkg/cli"
 	"github.com/docker/cagent/pkg/config"
@@ -27,7 +28,7 @@ type ToolOutput struct {
 }
 
 func StartMCPServer(ctx context.Context, out *cli.Printer, agentFilename string, runConfig config.RuntimeConfig) error {
-	slog.Debug("Starting MCP server", "agent_ref", agentFilename)
+	slog.Debug("Starting MCP server", "agent", agentFilename)
 
 	agentFilename, err := agentfile.Resolve(ctx, out, agentFilename)
 	if err != nil {
@@ -54,21 +55,29 @@ func StartMCPServer(ctx context.Context, out *cli.Printer, agentFilename string,
 	slog.Debug("Adding MCP tools for agents", "count", len(agentNames))
 
 	for _, agentName := range agentNames {
-		agent, err := t.Agent(agentName)
+		ag, err := t.Agent(agentName)
 		if err != nil {
 			return fmt.Errorf("failed to get agent %s: %w", agentName, err)
 		}
 
-		description := agent.Description()
+		description := ag.Description()
 		if description == "" {
 			description = fmt.Sprintf("Run the %s agent", agentName)
 		}
 
 		slog.Debug("Adding MCP tool", "agent", agentName, "description", description)
 
+		readOnly, err := isReadOnlyAgent(ctx, ag)
+		if err != nil {
+			return fmt.Errorf("failed to determine if agent %s is read-only: %w", agentName, err)
+		}
+
 		toolDef := &mcp.Tool{
-			Name:         agentName,
-			Description:  description,
+			Name:        agentName,
+			Description: description,
+			Annotations: &mcp.ToolAnnotations{
+				ReadOnlyHint: readOnly,
+			},
 			InputSchema:  tools.MustSchemaFor[ToolInput](),
 			OutputSchema: tools.MustSchemaFor[ToolOutput](),
 		}
@@ -89,14 +98,14 @@ func CreateToolHandler(t *team.Team, agentName, agentFilename string) func(conte
 	return func(ctx context.Context, req *mcp.CallToolRequest, input ToolInput) (*mcp.CallToolResult, ToolOutput, error) {
 		slog.Debug("MCP tool called", "agent", agentName, "message", input.Message)
 
-		agent, err := t.Agent(agentName)
+		ag, err := t.Agent(agentName)
 		if err != nil {
 			return nil, ToolOutput{}, fmt.Errorf("failed to get agent: %w", err)
 		}
 
 		sess := session.New(
 			session.WithTitle("MCP tool call"),
-			session.WithMaxIterations(agent.MaxIterations()),
+			session.WithMaxIterations(ag.MaxIterations()),
 			session.WithUserMessage(agentFilename, input.Message),
 			session.WithToolsApproved(true),
 		)
@@ -125,3 +134,18 @@ func CreateToolHandler(t *team.Team, agentName, agentFilename string) func(conte
 		return nil, ToolOutput{Response: result}, nil
 	}
 }
+
+func isReadOnlyAgent(ctx context.Context, ag *agent.Agent) (bool, error) {
+	allTolls, err := ag.Tools(ctx)
+	if err != nil {
+		return false, err
+	}
+
+	for _, tool := range allTolls {
+		if !tool.Annotations.ReadOnlyHint {
+			return false, nil
+		}
+	}
+
+	return true, nil
+}