feat(auth): track unique tools in access metrics

* Add tool tracking to AccessTracker and metrics
* Update tests to validate tool tracking functionality
* Modify middleware to record tool usage
* Enhance observability with tool context
* Update UI to display unique tools in metrics

internal/auth/keyring_test.go

@@ -1,6 +1,8 @@
 package auth
 
 import (
+	"bytes"
+	"encoding/json"
 	"io"
 	"log/slog"
 	"net/http"
@@ -8,6 +10,7 @@ import (
 	"testing"
 
 	"git.warky.dev/wdevs/amcs/internal/config"
+	"git.warky.dev/wdevs/amcs/internal/observability"
 )
 
 func testLogger() *slog.Logger {
@@ -188,3 +191,50 @@ func TestMiddlewareRecordsForwardedRemoteAddr(t *testing.T) {
 		t.Fatalf("snapshot remote_addr = %q, want %q", snap[0].RemoteAddr, "203.0.113.99")
 	}
 }
+
+func TestMiddlewareRecordsMCPToolUsage(t *testing.T) {
+	keyring, err := NewKeyring([]config.APIKey{{ID: "client-a", Value: "secret"}})
+	if err != nil {
+		t.Fatalf("NewKeyring() error = %v", err)
+	}
+	tracker := NewAccessTracker()
+	logger := testLogger()
+
+	authenticated := Middleware(config.AuthConfig{HeaderName: "x-brain-key"}, keyring, nil, nil, tracker, logger)(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusNoContent)
+	}))
+	handler := observability.AccessLog(logger)(authenticated)
+
+	payload := map[string]any{
+		"jsonrpc": "2.0",
+		"id":      "1",
+		"method":  "tools/call",
+		"params": map[string]any{
+			"name": "list_projects",
+		},
+	}
+	body, err := json.Marshal(payload)
+	if err != nil {
+		t.Fatalf("json.Marshal() error = %v", err)
+	}
+
+	req := httptest.NewRequest(http.MethodPost, "/mcp", bytes.NewReader(body))
+	req.Header.Set("x-brain-key", "secret")
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusNoContent {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusNoContent)
+	}
+
+	metrics := tracker.Metrics(10)
+	if metrics.UniqueTools != 1 {
+		t.Fatalf("UniqueTools = %d, want 1", metrics.UniqueTools)
+	}
+	if len(metrics.TopTools) != 1 {
+		t.Fatalf("len(TopTools) = %d, want 1", len(metrics.TopTools))
+	}
+	if metrics.TopTools[0].Key != "list_projects" || metrics.TopTools[0].RequestCount != 1 {
+		t.Fatalf("TopTools[0] = %+v, want list_projects with count 1", metrics.TopTools[0])
+	}
+}