fix(mcp): verify charger bindings through diagnostic reads

internal/mcp/api.go

@@ -18,7 +18,7 @@ func apiTools() []*tool {
 	return []*tool{
 		{
 			name: "api_catalog", title: "Start technical troubleshooting",
-			description: "For technical troubleshooting, start here. Ask the connected box for every diagnostic read it supports, its running version, source-code links and a workflow for collecting bug-report evidence. Includes energy logs, original measurements, planner snapshots, configuration, driver source, logs, support reports and exports. Ordinary status, history and control use the existing tools. The owner-approved diagnostic grant covers these reads; there are no extra endpoint permissions." + dataNote,
+			description: "For technical troubleshooting, start here. Ask the connected box for every diagnostic read it supports, its running version, source-code links and a workflow for collecting bug-report evidence. Newer boxes include charger_connections with exact saved driver names and configured, missing or unverified_ocpp status; configured means a name matches, not verified equipment. Includes energy logs, original measurements, planner snapshots, configuration, driver source, logs, support reports and exports. The basic config_get and drivers_status tools redact names and cannot verify charger bindings. Ordinary status, history and control use the existing tools. The owner-approved diagnostic grant covers these reads; there are no extra endpoint permissions." + dataNote,
 			scope:       readScope(protocol.MsgAPIRead), input: object(nil), readOnly: true,
 			run: func(ctx context.Context, cc *callCtx, args json.RawMessage) (any, error) {
 				if err := decodeArgs(args, &struct{}{}); err != nil {
@@ -119,7 +119,11 @@ func diagnosticAPIRead(ctx context.Context, cc *callCtx, read protocol.APIRead)
 	}
 	// Preserve the box's technical evidence, including exact json.Number
 	// values. Existing typed reads retain their own display sanitization.
-	return map[string]any{"path": read.Path, "status": head.Status, "response": data}, nil
+	result := map[string]any{"path": read.Path, "status": head.Status, "response": data}
+	if head.Status >= 400 {
+		return failedToolData{result}, nil
+	}
+	return result, nil
 }
 
 // apiRead collects the bounded api.* stream. A missing head, a skipped

internal/mcp/charger_diagnostics_test.go

@@ -0,0 +1,68 @@
+package mcp
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/srcfl/ftw-cloud/internal/oauth"
+	"github.com/srcfl/ftw/go/protocol"
+)
+
+func TestDiagnosticReadsPreserveAnOldChargerBindingForComparison(t *testing.T) {
+	world := newWorld(t)
+	box := world.connectBox()
+	assistant := world.connect(box, oauth.ScopeDiagRun)
+	read := func(path string) map[string]any {
+		t.Helper()
+		result, failed, _ := assistant.call("api_read", map[string]any{"path": path})
+		if failed {
+			t.Fatal("full diagnostic read failed")
+		}
+		transport := result["structuredContent"].(map[string]any)["data"].(map[string]any)
+		return transport["response"].(map[string]any)["body"].(map[string]any)
+	}
+	cfg := read("/api/config")
+	current := cfg["drivers"].([]any)[0].(map[string]any)["name"]
+	saved := cfg["loadpoints"].([]any)[0].(map[string]any)["driver_name"]
+	runtime := read("/api/drivers")["drivers"].([]any)[0].(map[string]any)["name"]
+	if current != "charger-current" || saved != "charger-old" || current != runtime {
+		t.Fatal("full diagnostic reads changed the names needed to identify an old binding")
+	}
+	_, _, asked := box.counts()
+	for _, request := range asked {
+		if strings.HasPrefix(request, protocol.MsgAPIReq+" ") {
+			t.Fatal("troubleshooting used an owner write path")
+		}
+	}
+}
+
+func TestRefusedDiagnosticReadIsAnErrorWithItsBoxEvidence(t *testing.T) {
+	world := newWorld(t)
+	assistant := world.connect(world.connectBox(), oauth.ScopeDiagRun)
+	result, failed, _ := assistant.call("api_read", map[string]any{"path": "/api/test/refused"})
+	if !failed {
+		t.Fatal("a refused diagnostic read looked successful")
+	}
+	transport := result["structuredContent"].(map[string]any)["data"].(map[string]any)
+	if transport["status"] != float64(403) || transport["response"].(map[string]any)["error"] != "diagnostic read refused" {
+		t.Fatal("the failed read lost its status or box evidence")
+	}
+}
+
+func TestTroubleshootingGuidanceUsesFullReadsAndStatesRedactionLimits(t *testing.T) {
+	for _, text := range []string{"api_catalog", "api_read", "config_get", "/api/config", "/api/drivers", "/api/loadpoints", "refused"} {
+		if !strings.Contains(Instructions, text) {
+			t.Errorf("missing troubleshooting guidance: %s", text)
+		}
+	}
+	server := &Server{tools: readTools()}
+	description := server.tool("config_get").description
+	if !strings.Contains(description, "cannot verify") || !strings.Contains(description, "redacted") {
+		t.Fatal("basic config tool does not state its diagnostic limit")
+	}
+	for _, tool := range []string{"api_read", "api_catalog"} {
+		if strings.Contains(description, tool) {
+			t.Fatal("the public basic tool recommends an unavailable tool")
+		}
+	}
+}

internal/mcp/e2e_test.go

@@ -551,6 +551,21 @@ func (b *stubBox) handle(s *boxSession, env appwire.Envelope) {
 		if q.Path == "/api/status" {
 			data, _ = json.Marshal(map[string]any{"text": strings.Repeat("x", 8000)})
 		}
+		status := http.StatusOK
+		switch q.Path {
+		case "/api/config":
+			data, _ = json.Marshal(map[string]any{"encoding": "json", "complete": true, "body": map[string]any{
+				"drivers":    []any{map[string]any{"name": "charger-current"}},
+				"loadpoints": []any{map[string]any{"id": "garage", "driver_name": "charger-old"}},
+			}})
+		case "/api/drivers":
+			data, _ = json.Marshal(map[string]any{"encoding": "json", "complete": true, "body": map[string]any{
+				"drivers": []any{map[string]any{"name": "charger-current", "status": "ok"}},
+			}})
+		case "/api/test/refused":
+			status = http.StatusForbidden
+			data, _ = json.Marshal(map[string]any{"error": "diagnostic read refused"})
+		}
 		if q.Path == protocol.AgentAPICatalogPath {
 			data = []byte(`{"routes":[{"path":"/api/energy/history"},{"path":"/api/series"},{"path":"/api/mpc/diagnose/at"},{"path":"/api/drivers/{id}/source"},{"path":"/api/future/read"}],"troubleshooting":{"core":{"version":"0.151.0-beta.1","source":"https://github.com/srcfl/ftw/tree/v0.151.0-beta.1"},"workflow":["Collect reproduction steps and incident time with timezone"]}}`)
 		}
@@ -569,7 +584,7 @@ func (b *stubBox) handle(s *boxSession, env appwire.Envelope) {
 		if truncated {
 			data = data[:q.MaxBytes]
 		}
-		b.reply(s, protocol.MsgAPIHead, env.ID, protocol.APIHeadMsg{Status: 200, Headers: map[string]string{"Content-Type": "application/json"}})
+		b.reply(s, protocol.MsgAPIHead, env.ID, protocol.APIHeadMsg{Status: status, Headers: map[string]string{"Content-Type": "application/json"}})
 		cut := len(data) / 2
 		b.mu.Lock()
 		badSequence := b.apiBadSequence

internal/mcp/mcp.go

@@ -62,7 +62,12 @@ const Instructions = "FTW Cloud reaches one home's FTW box as an assistant its o
 	"Setup edits need a separate owner-approved setup grant. Saving does not prove measurement or control on hardware. " +
 	"For ordinary status, history and control, use the existing tools. For technical troubleshooting, " +
 	"start with api_catalog: the box lists its full read API, running version, source-code links and " +
-	"steps for gathering bug-report evidence. api_read keeps technical identifiers, addresses, logs and source code."
+	"steps for gathering bug-report evidence. api_read keeps technical identifiers, addresses, logs and source code. " +
+	"For charger faults, check charger_connections when present, then read /api/config, /api/drivers and /api/loadpoints. " +
+	"Compare loadpoints[].driver_name with drivers[].name; when OCPP is enabled also read /api/ocpp/chargers. " +
+	"A missing saved binding is a configuration problem, not evidence that a vendor driver failed. " +
+	"config_get and drivers_status redact names and cannot verify these bindings. " +
+	"If a read is refused or unavailable, report the exact path and error and what remains unverified; never guess the missing result."
 
 // JSON-RPC and MCP error codes.
 const (

internal/mcp/public.go

@@ -16,6 +16,7 @@ const publicInstructions = "FTW reaches one home's box with its owner's approval
 	"from fresh measurements, power in W from energy in Wh, and plans from measured outcomes. " +
 	"Control needs a separate grant and the user's request; lasting changes wait for the owner. " +
 	"This connection cannot run arbitrary API reads, export backups or configure an installation. " +
+	"Redacted settings cannot verify exact charger-to-driver bindings; state that limit rather than guessing a driver fault. " +
 	"For a new installation, guide the user through FTW's maintained install documentation."
 
 // publicTool is an explicit list: a new tool needs review before this profile

internal/mcp/tools.go

@@ -403,7 +403,7 @@ func readTools() []*tool {
 		},
 		{
 			name: "config_get", title: "Settings",
-			description: "The box's configuration, redacted on the box: secrets, addresses and names removed. Without a section, the list of sections; with one, that section." + dataNote,
+			description: "A basic redacted settings overview. Secrets, addresses and names are removed or changed, so this result cannot verify a charger's exact driver binding. Full technical diagnostic reads, when this connection provides them, are needed for that comparison. Otherwise state what you cannot verify rather than attributing a fault to a driver. Without a section, the list of sections; with one, that section." + dataNote,
 			scope:       readScope(protocol.MsgConfigGet), readOnly: true,
 			input: object(map[string]any{
 				"section": map[string]any{"type": "string", "pattern": sectionName.String(), "maxLength": 64, "description": "One section, from the list. Leave out for the list."},