Expose discovered MCP tools through the act allowlist (#251)

Second half of the MCP client: the tools the manager discovers become rows in
the existing act allowlist instead of a parallel capability system.

An MCP tool is encoded in the columns that already exist — cmd
["mcp",<server>,<tool>], scope mcp:<server> — so no migration, and
ProposeTool/EnableTool/DisableTool, tool.Matcher and the confirm turn need no
changes. One branch in Executor.Exec routes such a row to the manager instead
of exec, and "mcp" is never run as a binary.

Discovery only ever PROPOSES. destructive comes from the inverse of the MCP
readOnlyHint, so a tool that does not promise to be read-only inherits the
confirm turn, and enabling stays on /tools behind step-up.

Voice args are positional and MCP args are named, so CallPositional binds only
what it can defend: no required properties runs bare, and a read-only tool with
exactly one required string or number gets the tail. Everything else refuses
with ErrNeedsArgs rather than guessing. The read-only condition was learned
against the live Vikunja server: update_task requires only task_id and takes
the rest as optional, so one guessed argument blanked the fields it did not
mention. A partially-filled write destroys what it omits, so a mutating tool
never receives a guessed argument.

Also: a read-only mcp_servers IPC method and an "MCP servers" card on /tools
showing transport, target and state, with the trust level of a local target
spelled out. There is deliberately no call-a-tool IPC method and no run button,
so mutation keeps exactly one path.

Vikunja #251

cmd/mavend/actions_act.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"log"
 
+	"github.com/kami/maven/internal/mcp"
 	"github.com/kami/maven/internal/router"
 	"github.com/kami/maven/internal/tool"
 )
@@ -52,6 +53,12 @@ func (h *reactiveHandler) actionAct(ctx context.Context, dec router.Decision) st
 			return "выполнить «" + phrase + "»? скажи «да» или «нет»."
 		case errors.Is(err, tool.ErrNotEnabled):
 			return h.proposeGap(ctx, dec)
+		case errors.Is(err, mcp.ErrNeedsArgs):
+			// An MCP tool that wants named arguments a spoken verb cannot
+			// supply. Guessing them would be a wrong act, so she says so
+			// instead — the tool is still runnable from the authed surface,
+			// where a human types them.
+			return "этому инструменту нужны аргументы, которые я из голоса не соберу — я не буду угадывать."
 		}
 		log.Printf("voice: tool %s: %v", dec.Slots.Fn, err)
 		if out != "" {

cmd/mavend/main.go

@@ -280,6 +280,9 @@ func run(args []string) error {
 			api := coreAPI.(*daemonAPI)
 			api.chatFn = voiceW.handler.handleText
 		}
+		if voiceW != nil && voiceW.mcp != nil {
+			coreAPI.(*daemonAPI).getMCPServers = voiceW.mcp.status
+		}
 	} else {
 		// locked mode: no real store yet, so there's no meaningful CoreAPI to
 		// serve. srv.Check below is the actual guard — every CoreAPI call is
@@ -518,6 +521,11 @@ func run(args []string) error {
 				}()
 			}
 
+			// Keep MCP connections alive (nil unless configured).
+			if voiceW != nil && voiceW.mcp != nil {
+				go voiceW.mcp.run(ctx)
+			}
+
 			dl.unlock()
 			log.Printf("mavend: unlocked via passkey assertion")
 			return nil
@@ -577,6 +585,13 @@ func run(args []string) error {
 				crawlWkr.run(ctx)
 			}()
 		}
+		if voiceW != nil && voiceW.mcp != nil {
+			wg.Add(1)
+			go func() {
+				defer wg.Done()
+				voiceW.mcp.run(ctx)
+			}()
+		}
 	}
 
 	<-ctx.Done()

cmd/mavend/mcp.go

@@ -0,0 +1,154 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/kami/maven/internal/config"
+	"github.com/kami/maven/internal/ipc"
+	"github.com/kami/maven/internal/mcp"
+	"github.com/kami/maven/internal/store"
+	"github.com/kami/maven/internal/webfetch"
+)
+
+// mcpRefreshInterval — how often the manager re-dials a server that is down.
+// The manager applies its own backoff on top, so this being short is cheap.
+const mcpRefreshInterval = time.Minute
+
+// mcpWiring — the MCP client, when the `mcp` block configures at least one
+// enabled server. nil ⇒ nothing was configured, nothing is connected, and an
+// allowlist row that happens to look like an MCP row refuses to run.
+//
+// It lives on the voice wiring because MCP tools ARE acts: they run through
+// tool.Executor, the enabled allowlist and the confirm turn, which only exist
+// on the voice/chat path. No voice surface ⇒ nothing that could call a tool.
+type mcpWiring struct {
+	mgr *mcp.Manager
+	st  *store.Store
+}
+
+// wireMCP builds the manager, connects, and proposes what it found. It never
+// fails the daemon: a server that is unreachable at boot is logged and retried,
+// because Maven starting is not contingent on someone else's process.
+func wireMCP(cfg *config.Config, st *store.Store) *mcpWiring {
+	servers := cfg.MCPServers()
+	if len(servers) == 0 {
+		return nil
+	}
+	limits := webfetch.Config{}
+	if cfg.MCP != nil {
+		limits.AllowHosts = cfg.MCP.AllowHosts
+		limits.DenyHosts = cfg.MCP.DenyHosts
+		limits.MaxBytes = cfg.MCP.MaxBytes
+		limits.Timeout = time.Duration(cfg.MCP.Timeout)
+	}
+	mgr, err := mcp.NewManager(mcp.WebfetchDoor(limits), servers)
+	if err != nil {
+		// Validation already ran in config.validate, so this is a programming
+		// error rather than a config one. Still not fatal: MCP off is a working
+		// Maven.
+		log.Printf("mcp: not wired: %v", err)
+		return nil
+	}
+	w := &mcpWiring{mgr: mgr, st: st}
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	mgr.Connect(ctx)
+	w.propose(ctx)
+	return w
+}
+
+// propose writes a 'proposed' allowlist row for every discovered tool. It does
+// NOT enable anything: a configured server is a place Maven may look, not a
+// capability she has. Kami enables what he wants on /tools, behind step-up,
+// which is the same gate a shell tool goes through.
+//
+// Re-running on every boot is idempotent — ProposeMCPTool never touches an
+// existing row, so a tool he disabled stays disabled and one he enabled keeps
+// the cmd he enabled it with.
+func (w *mcpWiring) propose(ctx context.Context) {
+	if w == nil {
+		return
+	}
+	now := time.Now()
+	fresh := 0
+	for _, t := range w.mgr.Tools() {
+		name := mcp.LocalName(t.Server, t.Name)
+		// No readOnlyHint ⇒ assume it mutates ⇒ the confirm turn. Being wrong
+		// in this direction only costs a question.
+		destructive := !t.ReadOnly
+		provenance := fmt.Sprintf("mcp %s/%s", t.Server, t.Name)
+		if t.Description != "" {
+			provenance += ": " + t.Description
+		}
+		ok, err := w.st.ProposeMCPTool(ctx, name, mcp.Scope(t.Server),
+			mcp.Cmd(t.Server, t.Name), destructive, provenance, now)
+		if err != nil {
+			log.Printf("mcp: propose %s: %v", name, err)
+			continue
+		}
+		if ok {
+			fresh++
+		}
+	}
+	if fresh > 0 {
+		log.Printf("mcp: %d new tool proposal(s) waiting on /tools", fresh)
+	}
+}
+
+// run re-dials downed servers and picks up tools that appeared, until ctx is
+// canceled.
+func (w *mcpWiring) run(ctx context.Context) {
+	if w == nil {
+		return
+	}
+	t := time.NewTicker(mcpRefreshInterval)
+	defer t.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-t.C:
+			w.mgr.Refresh(ctx)
+			w.propose(ctx)
+		}
+	}
+}
+
+// status maps the manager's view onto the wire type the web surface reads.
+func (w *mcpWiring) status() []ipc.MCPServerStatus {
+	if w == nil {
+		return nil
+	}
+	in := w.mgr.Status()
+	out := make([]ipc.MCPServerStatus, 0, len(in))
+	for _, s := range in {
+		out = append(out, ipc.MCPServerStatus{
+			Name:      s.Name,
+			Transport: s.Transport,
+			Target:    s.Target,
+			Connected: s.Connected,
+			Server:    s.Server,
+			Tools:     s.Tools,
+			Err:       s.Err,
+		})
+	}
+	return out
+}
+
+func (w *mcpWiring) close() {
+	if w == nil {
+		return
+	}
+	_ = w.mgr.Close()
+}
+
+// caller is the tool.MCPCaller the executor gets, or nil when MCP is off.
+func (w *mcpWiring) caller() *mcp.Manager {
+	if w == nil {
+		return nil
+	}
+	return w.mgr
+}

cmd/mavend/mcp_test.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"github.com/kami/maven/internal/config"
+)
+
+func TestWireMCPOffWhenUnconfigured(t *testing.T) {
+	st := newTestStore(t)
+	for name, cfg := range map[string]*config.Config{
+		"no block": {},
+		"nothing enabled": {MCP: &config.MCPConfig{Servers: []config.MCPServerConfig{
+			{Name: "vikunja", URL: "http://192.168.1.104:9100/mcp"},
+		}}},
+	} {
+		t.Run(name, func(t *testing.T) {
+			if w := wireMCP(cfg, st); w != nil {
+				t.Fatal("MCP must be off unless a server is configured AND enabled")
+			}
+		})
+	}
+	// nil wiring must be safe to use everywhere it is reachable.
+	var w *mcpWiring
+	w.close()
+	w.propose(context.Background())
+	if w.status() != nil || w.caller() != nil {
+		t.Fatal("a nil wiring must report nothing")
+	}
+}
+
+// An unreachable server must not stop the daemon, must be reported as down, and
+// must propose nothing.
+func TestWireMCPUnreachableServerIsNotFatal(t *testing.T) {
+	st := newTestStore(t)
+	w := wireMCP(&config.Config{MCP: &config.MCPConfig{Servers: []config.MCPServerConfig{{
+		Name: "dead", Command: "/nonexistent/mcp-server", Enabled: true,
+	}}}}, st)
+	if w == nil {
+		t.Fatal("a configured server should still wire")
+	}
+	defer w.close()
+	st2 := w.status()
+	if len(st2) != 1 || st2[0].Connected || st2[0].Err == "" {
+		t.Fatalf("status = %+v", st2)
+	}
+	tools, err := st.ListTools(context.Background(), "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(tools) != 0 {
+		t.Fatalf("a server that never answered must propose nothing, got %+v", tools)
+	}
+}
+
+// A url server whose address is private is refused by webfetch unless that
+// server sets allow_private. This is the guard the whole MCP path rides on, so
+// it is asserted here too, at the wiring level.
+func TestWireMCPPrivateURLRefusedWithoutAllowPrivate(t *testing.T) {
+	st := newTestStore(t)
+	w := wireMCP(&config.Config{MCP: &config.MCPConfig{Servers: []config.MCPServerConfig{{
+		Name: "lan", URL: "http://127.0.0.1:9100/mcp", Enabled: true,
+	}}}}, st)
+	if w == nil {
+		t.Fatal("should wire")
+	}
+	defer w.close()
+	s := w.status()[0]
+	if s.Connected {
+		t.Fatal("a loopback server must not connect without allow_private")
+	}
+	if !strings.Contains(s.Err, "private address") {
+		t.Fatalf("err = %q, want the private-address refusal", s.Err)
+	}
+}

cmd/mavend/tick.go

@@ -941,6 +941,7 @@ type daemonAPI struct {
 	getMorningStatus func(ctx context.Context) []ipc.MorningRoutineStatus
 	getDayPlan       func(ctx context.Context) ipc.DayPlan
 	chatFn           func(ctx context.Context, text string) string
+	getMCPServers    func() []ipc.MCPServerStatus
 }
 
 func (d *daemonAPI) Chat(ctx context.Context, text string) (string, error) {
@@ -950,6 +951,16 @@ func (d *daemonAPI) Chat(ctx context.Context, text string) (string, error) {
 	return d.chatFn(ctx, text), nil
 }
 
+// MCPServers — the configured MCP servers and their health (Vikunja #251).
+// Empty, not an error, when the mcp block is absent: "not configured" is the
+// default state and the web surface renders it as such.
+func (d *daemonAPI) MCPServers(ctx context.Context) ([]ipc.MCPServerStatus, error) {
+	if d.getMCPServers == nil {
+		return nil, nil
+	}
+	return d.getMCPServers(), nil
+}
+
 func (d *daemonAPI) TickTrace(ctx context.Context) (ipc.TickTrace, error) {
 	trace := d.getTrace()
 	if trace == nil {

cmd/mavend/voicewire.go

@@ -40,6 +40,10 @@ type voiceWiring struct {
 	// mavsttd / mavttsd don't keep a stale conn into a restarting daemon.
 	sttClient *worker.Client
 	ttsClient *worker.Client
+	// mcp — the MCP client, nil unless the `mcp` block configures an enabled
+	// server (Vikunja #251). Its tools land in the same allowlist as every
+	// other act, so nothing else here has to know about it.
+	mcp *mcpWiring
 }
 
 // close releases the listener + worker conns. Safe to call on nil (when
@@ -60,6 +64,7 @@ func (w *voiceWiring) close() {
 	if w.ttsClient != nil {
 		_ = w.ttsClient.Close()
 	}
+	w.mcp.close()
 }
 
 // wireVoice builds the audio path from cfg + a CoreAPI + a router. Returns
@@ -131,6 +136,14 @@ func wireVoice(cfg *config.Config, coreAPI ipc.CoreAPI, phr phraser.Phraser, mem
 	// daemon restart.
 	seedTools(coreAPI, cfg.Voice.Tools)
 	exec := tool.NewExecutor(coreAPI, time.Duration(cfg.Voice.ToolTimeout))
+	// MCP servers (Vikunja #251): discovery PROPOSES tools into the same
+	// allowlist, so an MCP tool is enabled by hand on /tools like any other and
+	// runs through the same confirm turn. Off unless the `mcp` block configures
+	// an enabled server.
+	w.mcp = wireMCP(cfg, dataStore)
+	if w.mcp != nil {
+		exec = exec.WithMCP(w.mcp.caller())
+	}
 	matcher := tool.NewMatcher(coreAPI)
 
 	// ----- weather provider (Open-Meteo when configured, Stub otherwise) -----

cmd/mavweb/handlers_test.go

@@ -67,6 +67,14 @@ type fakeCore struct {
 	// for handleChatAPI tests
 	chatText string
 	chatErr  error
+
+	// for the MCP section of /tools
+	mcpServers []ipc.MCPServerStatus
+	mcpErr     error
+}
+
+func (f *fakeCore) MCPServers(context.Context) ([]ipc.MCPServerStatus, error) {
+	return f.mcpServers, f.mcpErr
 }
 
 func (f *fakeCore) Chat(_ context.Context, text string) (string, error) {
@@ -1118,3 +1126,49 @@ func TestHandleChatAPI_FailOpenByDefault(t *testing.T) {
 		t.Errorf("core.Chat text = %q, want %q", core.chatText, "привет")
 	}
 }
+
+// The MCP section renders the configured servers, and a proposal that already
+// knows its cmd prefills the enable form so the argv is not retyped by hand.
+func TestHandleTools_GET_MCPSection(t *testing.T) {
+	core := &fakeCore{
+		proposed: []ipc.Tool{{
+			Name: "vikunja_list_tasks", Scope: "mcp:vikunja",
+			Cmd: []string{"mcp", "vikunja", "list_tasks"}, Destructive: true,
+			Utterance: "mcp vikunja/list_tasks: List tasks in a project.",
+		}},
+		mcpServers: []ipc.MCPServerStatus{
+			{Name: "vikunja", Transport: "http", Target: "http://192.168.1.104:9100/mcp", Connected: true, Server: "vikunja 0.1.0", Tools: 4},
+			{Name: "files", Transport: "stdio", Target: "mcp-server-fs /srv", Err: "start: no such file"},
+		},
+	}
+	rr := httptest.NewRecorder()
+	handleTools(rr, httptest.NewRequest(http.MethodGet, "/tools", nil), core, nil, false)
+	if rr.Code != http.StatusOK {
+		t.Fatalf("status = %d", rr.Code)
+	}
+	body := rr.Body.String()
+	for _, want := range []string{
+		"MCP servers", "vikunja", "192.168.1.104:9100/mcp", "vikunja 0.1.0",
+		"files", "no such file",
+		`value="mcp vikunja list_tasks"`, // the enable form is prefilled
+		"checked",                        // and pre-marked destructive (no readOnlyHint)
+	} {
+		if !strings.Contains(body, want) {
+			t.Errorf("missing %q in /tools output", want)
+		}
+	}
+}
+
+// MCP off (or an older core that does not know the method) renders the section
+// empty instead of breaking the page.
+func TestHandleTools_GET_MCPUnavailable(t *testing.T) {
+	core := &fakeCore{mcpErr: ipc.ErrNotImplemented}
+	rr := httptest.NewRecorder()
+	handleTools(rr, httptest.NewRequest(http.MethodGet, "/tools", nil), core, nil, false)
+	if rr.Code != http.StatusOK {
+		t.Fatalf("status = %d, want 200", rr.Code)
+	}
+	if !strings.Contains(rr.Body.String(), "no MCP servers configured") {
+		t.Error("expected the empty-state copy")
+	}
+}

cmd/mavweb/main.go

@@ -692,7 +692,7 @@ const toolsHTML = `{{template "shellTop" "tools"}}
 {{if .Msg}}<div class="msg msg-ok">{{.Msg}}</div>{{end}}
 <section class=card>
 <h2 class=card-title>proposed <span class=badge>{{len .Proposed}}</span></h2>
-{{if .Proposed}}<p class=hint>maven drafted these from acts she couldn't run. Fill the command (argv, space-separated) and enable.</p>
+{{if .Proposed}}<p class=hint>maven drafted these from acts she couldn't run. Fill the command (argv, space-separated) and enable. A row in an <code>mcp:</code> scope came from an MCP server and already knows what it calls — check the command, then enable.</p>
 <div class=scroll><table><tr><th>name</th><th>scope</th><th>from utterance</th><th>enable as</th></tr>
 {{range .Proposed}}<tr>
 <td><code>{{.Name}}</code></td><td><span class=badge>{{.Scope}}</span></td><td>{{.Utterance}}</td>
@@ -700,8 +700,8 @@ const toolsHTML = `{{template "shellTop" "tools"}}
 <input type=hidden name=name value="{{.Name}}">
 <input type=hidden name=scope value="{{.Scope}}">
 <input type=hidden name=action value=enable>
-<input type=text name=cmd class=input-wide placeholder="systemctl restart" required>
-<label><input type=checkbox name=destructive> destructive</label>
+<input type=text name=cmd class=input-wide placeholder="systemctl restart" value="{{join .Cmd " "}}" required>
+<label><input type=checkbox name=destructive {{if .Destructive}}checked{{end}}> destructive</label>
 <button class=btn>enable</button></form>
 <form method=post action=/tools class=inline-form>
 <input type=hidden name=name value="{{.Name}}">
@@ -730,6 +730,19 @@ const toolsHTML = `{{template "shellTop" "tools"}}
   <div class=hint>enable proposed tools above, or ask maven to configure one</div>
 </div>{{end}}
 </section>
+<section class=card>
+<h2 class=card-title>MCP servers <span class=badge>{{len .MCP}}</span></h2>
+{{if .MCP}}<p class=hint>servers she connects OUT to. Their tools appear above as proposals — a configured server is a place she may look, not a capability she has. A <code>stdio</code> target is a process on this box; an <code>http</code> one on a loopback or LAN address is inside the network, so treat its tools accordingly.</p>
+<div class=scroll><table><tr><th>name</th><th>transport</th><th>target</th><th>state</th><th>tools</th></tr>
+{{range .MCP}}<tr><td><code>{{.Name}}</code></td><td><span class=badge>{{.Transport}}</span></td><td><code>{{.Target}}</code></td>
+<td>{{if .Connected}}connected{{if .Server}} — {{.Server}}{{end}}{{else}}<span class=red>down</span>{{if .Err}} — {{.Err}}{{end}}{{end}}</td>
+<td>{{.Tools}}</td></tr>{{end}}</table></div>
+{{else}}<div class=empty>
+  <svg class=icon width="20" height="20"><use href="/ethos-icons.svg#i-settings"/></svg>
+  <div>no MCP servers configured</div>
+  <div class=hint>add an <code>mcp.servers</code> block to mavend.json to let her use an external tool server</div>
+</div>{{end}}
+</section>
 {{template "shellBottom"}}`
 
 // routinesHTML — proposed routine review surface. One row per thing maven
@@ -1320,12 +1333,20 @@ func handleTools(w http.ResponseWriter, r *http.Request, core ipc.CoreAPI, sessi
 		http.Error(w, "core read failed", http.StatusBadGateway)
 		return
 	}
+	// MCP is off by default and an older core may not know the method at all,
+	// so a failure here renders an empty section rather than breaking the page.
+	servers, err := core.MCPServers(ctx)
+	if err != nil {
+		log.Printf("tools: mcp servers: %v", err)
+		servers = nil
+	}
 	w.Header().Set("Content-Type", "text/html; charset=utf-8")
 	if err := toolsTmpl.Execute(w, struct {
 		Msg      string
 		Proposed []ipc.Tool
 		Enabled  []ipc.Tool
-	}{msg, proposed, enabled}); err != nil {
+		MCP      []ipc.MCPServerStatus
+	}{msg, proposed, enabled, servers}); err != nil {
 		log.Printf("tools render: %v", err)
 	}
 }