Restore MCP server support alongside built-in execute_code

Bring back ollie/mcp and ollie/tools packages. Config MCPServers
field restored. MCP tools are discovered at startup and added to
the agent tool list alongside execute_code. Dispatch routes by
server name for MCP tools, falls back to built-in execute_code.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

config/config.go

@@ -6,7 +6,15 @@ import (
 )
 
 type Config struct {
-	Hooks map[string]string `json:"hooks,omitempty"`
+	MCPServers map[string]ServerConfig `json:"mcpServers,omitempty"`
+	Hooks      map[string]string       `json:"hooks,omitempty"`
+}
+
+type ServerConfig struct {
+	Command  string            `json:"command,omitempty"`
+	Args     []string          `json:"args,omitempty"`
+	Env      map[string]string `json:"env,omitempty"`
+	Disabled bool              `json:"disabled,omitempty"`
 }
 
 func Load(path string) (*Config, error) {

main.go

@@ -18,6 +18,8 @@ import (
 	"ollie/backend"
 	"ollie/config"
 	execpkg "ollie/exec"
+	"ollie/mcp"
+	"ollie/tools"
 )
 
 const systemPrompt = `You are an autonomous agent. You have one tool: execute_code.
@@ -123,6 +125,7 @@ func main() {
 	}
 
 	hooks := make(map[string]string)
+	var cfg *config.Config
 	cfgPath := ""
 	if len(os.Args) > 2 {
 		cfgPath = os.Args[2]
@@ -130,15 +133,41 @@ func main() {
 		home, _ := os.UserHomeDir()
 		cfgPath = home + "/.config/ollie/config.json"
 	}
-	if cfg, err := config.Load(cfgPath); err == nil {
+	if c, err := config.Load(cfgPath); err == nil {
+		cfg = c
 		if cfg.Hooks != nil {
 			hooks = cfg.Hooks
 		}
 	} else if len(os.Args) > 2 {
-		// Only fatal if the path was explicitly provided.
 		log.Fatalf("Failed to load config: %v", err)
 	}
 
+	// Connect MCP servers.
+	mcpExec := tools.NewExecutor()
+	if cfg != nil {
+		for name, serverCfg := range cfg.MCPServers {
+			if serverCfg.Disabled || serverCfg.Command == "" {
+				continue
+			}
+			transport := mcp.NewSTDIOTransport(serverCfg.Command, serverCfg.Args, serverCfg.Env)
+			client, err := transport.Connect()
+			if err != nil {
+				log.Printf("Failed to connect to MCP server %s: %v", name, err)
+				continue
+			}
+			mcpExec.AddServer(name, client)
+			log.Printf("Connected to MCP server: %s", name)
+		}
+	}
+
+	mcpTools, err := mcpExec.ListTools()
+	if err != nil {
+		log.Fatalf("Failed to list MCP tools: %v", err)
+	}
+	if len(mcpTools) > 0 {
+		log.Printf("Loaded %d MCP tools", len(mcpTools))
+	}
+
 	be, err := backend.New()
 	if err != nil {
 		log.Fatalf("Failed to create backend: %v", err)
@@ -150,12 +179,25 @@ func main() {
 		home+"/.cache/ollie/exec",
 	)
 
+	allTools := append(mcpToolsToBackend(mcpTools), executeCodeTool)
+	serverOf := make(map[string]string, len(mcpTools))
+	for _, t := range mcpTools {
+		serverOf[t.Name] = t.Server
+	}
+
 	loopcfg := agent.Config{
 		Backend:      be,
 		Model:        modelName,
 		SystemPrompt: systemPrompt,
-		Tools:        []backend.Tool{executeCodeTool},
-		Exec:     func(name string, args json.RawMessage) (string, error) {
+		Tools:        allTools,
+		Exec: func(name string, args json.RawMessage) (string, error) {
+			if server, ok := serverOf[name]; ok {
+				raw, err := mcpExec.Execute(server, name, args)
+				if err != nil {
+					return "", err
+				}
+				return extractMCPText(raw), nil
+			}
 			if name == "execute_code" {
 				return dispatchBuiltinExec(builtinExec, args)
 			}
@@ -356,6 +398,39 @@ func wordWrap(s string, width int) string {
 
 // -- tool helpers --
 
+// mcpToolsToBackend converts MCP tool descriptors to backend.Tool entries.
+func mcpToolsToBackend(mcpTools []tools.ToolInfo) []backend.Tool {
+	out := make([]backend.Tool, len(mcpTools))
+	for i, t := range mcpTools {
+		out[i] = backend.Tool{
+			Name:        t.Name,
+			Description: t.Description,
+			Parameters:  t.InputSchema,
+		}
+	}
+	return out
+}
+
+// extractMCPText unwraps {"content":[{"type":"text","text":"..."}]}.
+func extractMCPText(raw json.RawMessage) string {
+	var result struct {
+		Content []struct {
+			Type string `json:"type"`
+			Text string `json:"text"`
+		} `json:"content"`
+	}
+	if err := json.Unmarshal(raw, &result); err != nil {
+		return string(raw)
+	}
+	var parts []string
+	for _, c := range result.Content {
+		if c.Type == "text" {
+			parts = append(parts, c.Text)
+		}
+	}
+	return strings.Join(parts, "\n")
+}
+
 // dispatchBuiltinExec handles execute_code natively.
 func dispatchBuiltinExec(e *execpkg.Executor, args json.RawMessage) (string, error) {
 	var a struct {

mcp/client.go

@@ -0,0 +1,82 @@
+package mcp
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"io"
+	"sync"
+)
+
+// Message is a JSON-RPC 2.0 message.
+type Message struct {
+	JSONRPC string          `json:"jsonrpc"`
+	ID      int             `json:"id,omitempty"`
+	Method  string          `json:"method,omitempty"`
+	Params  interface{}     `json:"params,omitempty"`
+	Result  json.RawMessage `json:"result,omitempty"`
+	Error   *RPCError       `json:"error,omitempty"`
+}
+
+// RPCError is a JSON-RPC error object.
+type RPCError struct {
+	Code    int    `json:"code"`
+	Message string `json:"message"`
+}
+
+func (e *RPCError) Error() string {
+	return fmt.Sprintf("rpc error %d: %s", e.Code, e.Message)
+}
+
+// Client is a JSON-RPC client over a pair of streams (typically stdin/stdout
+// of a subprocess).
+type Client struct {
+	mu     sync.Mutex
+	w      io.Writer
+	sc     *bufio.Scanner
+	nextID int
+}
+
+// NewClient creates a Client from a reader and writer.
+func NewClient(r io.Reader, w io.Writer) *Client {
+	return &Client{w: w, sc: bufio.NewScanner(r)}
+}
+
+// Call sends a JSON-RPC request and returns the result.
+func (c *Client) Call(method string, params interface{}) (json.RawMessage, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	c.nextID++
+	id := c.nextID
+
+	msg := Message{
+		JSONRPC: "2.0",
+		ID:      id,
+		Method:  method,
+		Params:  params,
+	}
+	data, err := json.Marshal(msg)
+	if err != nil {
+		return nil, err
+	}
+	if _, err := fmt.Fprintf(c.w, "%s\n", data); err != nil {
+		return nil, err
+	}
+
+	if !c.sc.Scan() {
+		if err := c.sc.Err(); err != nil {
+			return nil, err
+		}
+		return nil, io.EOF
+	}
+
+	var resp Message
+	if err := json.Unmarshal(c.sc.Bytes(), &resp); err != nil {
+		return nil, err
+	}
+	if resp.Error != nil {
+		return nil, resp.Error
+	}
+	return resp.Result, nil
+}

mcp/transport.go

@@ -0,0 +1,56 @@
+package mcp
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+)
+
+// STDIOTransport launches a subprocess and connects a Client to its stdin/stdout.
+type STDIOTransport struct {
+	command string
+	args    []string
+	env     map[string]string
+}
+
+// NewSTDIOTransport creates a transport that will launch the given command.
+func NewSTDIOTransport(command string, args []string, env map[string]string) *STDIOTransport {
+	return &STDIOTransport{command: command, args: args, env: env}
+}
+
+// Connect launches the subprocess and returns a connected Client.
+func (t *STDIOTransport) Connect() (*Client, error) {
+	cmd := exec.Command(t.command, t.args...)
+	for k, v := range t.env {
+		cmd.Env = append(os.Environ(), fmt.Sprintf("%s=%s", k, v))
+	}
+
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		return nil, err
+	}
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, err
+	}
+	if err := cmd.Start(); err != nil {
+		return nil, err
+	}
+
+	client := NewClient(stdout, stdin)
+
+	// MCP initialization handshake.
+	if _, err := client.Call("initialize", map[string]interface{}{
+		"protocolVersion": "2024-11-05",
+		"capabilities":    map[string]interface{}{},
+		"clientInfo":      map[string]interface{}{"name": "ollie", "version": "0.1"},
+	}); err != nil {
+		return nil, fmt.Errorf("initialize: %w", err)
+	}
+	if _, err := client.Call("notifications/initialized", nil); err != nil {
+		// Some servers don't respond to this notification; ignore errors.
+		_ = err
+	}
+
+	return client, nil
+}

mcpconfig.json

@@ -1,11 +1,5 @@
 {
   "globalShortcut": "Ctrl+Space",
-  "mcpServers": {
-  "anvilmcp": {
-      "command": "anvilmcp",
-      "args": []
-    }
-  },
   "hooks": {
     "agentSpawn": "anvillm-hook agentSpawn",
     "userPromptSubmit": "anvillm-hook userPromptSubmit",

tools/executor.go

@@ -0,0 +1,72 @@
+package tools
+
+import (
+	"encoding/json"
+	"fmt"
+	"ollie/mcp"
+)
+
+// ToolInfo describes a tool provided by an MCP server.
+type ToolInfo struct {
+	Server      string
+	Name        string
+	Description string
+	InputSchema json.RawMessage
+}
+
+// Executor routes tool calls to the MCP server that owns them.
+type Executor struct {
+	servers map[string]*mcp.Client
+}
+
+// NewExecutor creates an empty Executor.
+func NewExecutor() *Executor {
+	return &Executor{servers: make(map[string]*mcp.Client)}
+}
+
+// AddServer registers an MCP client under the given name.
+func (e *Executor) AddServer(name string, client *mcp.Client) {
+	e.servers[name] = client
+}
+
+// ListTools returns all tools advertised by all connected servers.
+func (e *Executor) ListTools() ([]ToolInfo, error) {
+	var all []ToolInfo
+	for serverName, client := range e.servers {
+		result, err := client.Call("tools/list", nil)
+		if err != nil {
+			return nil, fmt.Errorf("server %s: %w", serverName, err)
+		}
+		var resp struct {
+			Tools []struct {
+				Name        string          `json:"name"`
+				Description string          `json:"description"`
+				InputSchema json.RawMessage `json:"inputSchema"`
+			} `json:"tools"`
+		}
+		if err := json.Unmarshal(result, &resp); err != nil {
+			return nil, err
+		}
+		for _, t := range resp.Tools {
+			all = append(all, ToolInfo{
+				Server:      serverName,
+				Name:        t.Name,
+				Description: t.Description,
+				InputSchema: t.InputSchema,
+			})
+		}
+	}
+	return all, nil
+}
+
+// Execute calls a named tool on the named server.
+func (e *Executor) Execute(serverName, toolName string, args json.RawMessage) (json.RawMessage, error) {
+	client, ok := e.servers[serverName]
+	if !ok {
+		return nil, fmt.Errorf("server not found: %s", serverName)
+	}
+	return client.Call("tools/call", map[string]any{
+		"name":      toolName,
+		"arguments": args,
+	})
+}