diff --git a/AGENTS.md b/AGENTS.md
index ead439f1b..0f9a8f332 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -12,7 +12,7 @@ agentmemory is a persistent memory system for AI coding agents, built on iii-eng
 ## Consistency Rules
 
 **When adding or removing MCP tools, you MUST update ALL of the following:**
-1. `src/mcp/tools-registry.ts` — tool definition + `getAllTools()` array
+1. `src/mcp/tools-registry.ts` — tool definition + `getAllTools()` array (every tool must include `annotations` with `readOnlyHint`/`destructiveHint`: read-only tools get `readOnlyHint: true`, destructive tools get `destructiveHint: true`)
 2. `src/mcp/server.ts` — handler case in the `mcp::tools::call` switch
 3. `src/triggers/api.ts` — REST endpoint registration
 4. `src/index.ts` — function registration + endpoint count in the log line
diff --git a/src/mcp/tools-registry.ts b/src/mcp/tools-registry.ts
index c4df3499c..f787edefb 100644
--- a/src/mcp/tools-registry.ts
+++ b/src/mcp/tools-registry.ts
@@ -1,3 +1,11 @@
+export type McpToolAnnotations = {
+  readOnlyHint?: boolean;
+  destructiveHint?: boolean;
+  idempotentHint?: boolean;
+  openWorldHint?: boolean;
+  title?: string;
+};
+
 export type McpToolDef = {
   name: string;
   description: string;
@@ -6,6 +14,7 @@ export type McpToolDef = {
     properties: Record<string, { type: string; description: string }>;
     required?: string[];
   };
+  annotations?: McpToolAnnotations;
 };
 
 export const CORE_TOOLS: McpToolDef[] = [
@@ -35,6 +44,7 @@ export const CORE_TOOLS: McpToolDef[] = [
       },
       required: ["query"],
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_compress_file",
@@ -50,6 +60,7 @@ export const CORE_TOOLS: McpToolDef[] = [
       },
       required: ["filePath"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_save",
@@ -86,6 +97,7 @@ export const CORE_TOOLS: McpToolDef[] = [
       },
       required: ["content"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_file_history",
@@ -101,6 +113,7 @@ export const CORE_TOOLS: McpToolDef[] = [
       },
       required: ["files"],
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_patterns",
@@ -111,12 +124,14 @@ export const CORE_TOOLS: McpToolDef[] = [
         project: { type: "string", description: "Project path to analyze" },
       },
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_sessions",
     description:
       "List recent sessions with their status and observation counts.",
     inputSchema: { type: "object", properties: {} },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_smart_search",
@@ -133,6 +148,7 @@ export const CORE_TOOLS: McpToolDef[] = [
       },
       required: ["query"],
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_vision_search",
@@ -148,6 +164,7 @@ export const CORE_TOOLS: McpToolDef[] = [
         sessionId: { type: "string", description: "Filter to a single session" },
       },
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_timeline",
@@ -171,6 +188,7 @@ export const CORE_TOOLS: McpToolDef[] = [
       },
       required: ["anchor"],
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_profile",
@@ -186,11 +204,13 @@ export const CORE_TOOLS: McpToolDef[] = [
       },
       required: ["project"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_export",
     description: "Export all memory data as JSON.",
     inputSchema: { type: "object", properties: {} },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_relations",
@@ -213,6 +233,7 @@ export const CORE_TOOLS: McpToolDef[] = [
       },
       required: ["memoryId"],
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_commit_lookup",
@@ -225,6 +246,7 @@ export const CORE_TOOLS: McpToolDef[] = [
       },
       required: ["sha"],
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_commits",
@@ -238,6 +260,7 @@ export const CORE_TOOLS: McpToolDef[] = [
         limit: { type: "number", description: "Max results (default 100, max 500)" },
       },
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
 ];
 
@@ -257,6 +280,7 @@ export const V040_TOOLS: McpToolDef[] = [
       },
       required: ["direction"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_graph_query",
@@ -276,6 +300,7 @@ export const V040_TOOLS: McpToolDef[] = [
         query: { type: "string", description: "Search nodes by name" },
       },
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_consolidate",
@@ -290,6 +315,7 @@ export const V040_TOOLS: McpToolDef[] = [
         },
       },
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_team_share",
@@ -308,6 +334,7 @@ export const V040_TOOLS: McpToolDef[] = [
       },
       required: ["itemId", "itemType"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_team_feed",
@@ -318,6 +345,7 @@ export const V040_TOOLS: McpToolDef[] = [
         limit: { type: "number", description: "Max items (default 20)" },
       },
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_audit",
@@ -329,6 +357,7 @@ export const V040_TOOLS: McpToolDef[] = [
         limit: { type: "number", description: "Max entries (default 50)" },
       },
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_governance_delete",
@@ -344,6 +373,7 @@ export const V040_TOOLS: McpToolDef[] = [
       },
       required: ["memoryIds"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: true },
   },
   {
     name: "memory_snapshot_create",
@@ -354,6 +384,7 @@ export const V040_TOOLS: McpToolDef[] = [
         message: { type: "string", description: "Snapshot description" },
       },
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
 ];
 
@@ -391,6 +422,7 @@ export const V050_TOOLS: McpToolDef[] = [
       },
       required: ["title"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_action_update",
@@ -412,6 +444,7 @@ export const V050_TOOLS: McpToolDef[] = [
       },
       required: ["actionId"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_frontier",
@@ -428,6 +461,7 @@ export const V050_TOOLS: McpToolDef[] = [
         limit: { type: "number", description: "Max results (default 20)" },
       },
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_next",
@@ -440,6 +474,7 @@ export const V050_TOOLS: McpToolDef[] = [
         agentId: { type: "string", description: "Current agent ID" },
       },
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_lease",
@@ -465,6 +500,7 @@ export const V050_TOOLS: McpToolDef[] = [
       },
       required: ["actionId", "agentId", "operation"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_routine_run",
@@ -479,6 +515,7 @@ export const V050_TOOLS: McpToolDef[] = [
       },
       required: ["routineId"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_signal_send",
@@ -504,6 +541,7 @@ export const V050_TOOLS: McpToolDef[] = [
       },
       required: ["from", "content"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_signal_read",
@@ -525,6 +563,7 @@ export const V050_TOOLS: McpToolDef[] = [
       },
       required: ["agentId"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_checkpoint",
@@ -558,6 +597,7 @@ export const V050_TOOLS: McpToolDef[] = [
       },
       required: ["operation"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_mesh_sync",
@@ -576,6 +616,7 @@ export const V050_TOOLS: McpToolDef[] = [
         },
       },
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
 ];
 
@@ -604,6 +645,7 @@ export const V051_TOOLS: McpToolDef[] = [
       },
       required: ["name", "type"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_sentinel_trigger",
@@ -617,6 +659,7 @@ export const V051_TOOLS: McpToolDef[] = [
       },
       required: ["sentinelId"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_sketch_create",
@@ -632,6 +675,7 @@ export const V051_TOOLS: McpToolDef[] = [
       },
       required: ["title"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_sketch_promote",
@@ -645,6 +689,7 @@ export const V051_TOOLS: McpToolDef[] = [
       },
       required: ["sketchId"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_crystallize",
@@ -662,6 +707,7 @@ export const V051_TOOLS: McpToolDef[] = [
       },
       required: ["actionIds"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_diagnose",
@@ -676,6 +722,7 @@ export const V051_TOOLS: McpToolDef[] = [
         },
       },
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_heal",
@@ -694,6 +741,7 @@ export const V051_TOOLS: McpToolDef[] = [
         },
       },
     },
+    annotations: { readOnlyHint: false, destructiveHint: true },
   },
   {
     name: "memory_facet_tag",
@@ -712,6 +760,7 @@ export const V051_TOOLS: McpToolDef[] = [
       },
       required: ["targetId", "targetType", "dimension", "value"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_facet_query",
@@ -734,6 +783,7 @@ export const V051_TOOLS: McpToolDef[] = [
         },
       },
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
 ];
 
@@ -752,6 +802,7 @@ export const V061_TOOLS: McpToolDef[] = [
       },
       required: ["id"],
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
 ];
 
@@ -780,6 +831,7 @@ export const V070_TOOLS: McpToolDef[] = [
       },
       required: ["content"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_lesson_recall",
@@ -798,6 +850,7 @@ export const V070_TOOLS: McpToolDef[] = [
       },
       required: ["query"],
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_obsidian_export",
@@ -816,6 +869,7 @@ export const V070_TOOLS: McpToolDef[] = [
         },
       },
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
 ];
 
@@ -834,6 +888,7 @@ export const V073_TOOLS: McpToolDef[] = [
         },
       },
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_insight_list",
@@ -850,6 +905,7 @@ export const V073_TOOLS: McpToolDef[] = [
         limit: { type: "number", description: "Max results (default 50)" },
       },
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
 ];
 
@@ -859,6 +915,7 @@ export const V010_SLOTS_TOOLS: McpToolDef[] = [
     description:
       "List all memory slots (pinned + project + global). Slots are editable, size-limited memory units the agent can read and modify across sessions.",
     inputSchema: { type: "object", properties: {} },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_slot_get",
@@ -870,6 +927,7 @@ export const V010_SLOTS_TOOLS: McpToolDef[] = [
       },
       required: ["label"],
     },
+    annotations: { readOnlyHint: true, destructiveHint: false },
   },
   {
     name: "memory_slot_create",
@@ -886,6 +944,7 @@ export const V010_SLOTS_TOOLS: McpToolDef[] = [
       },
       required: ["label"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_slot_append",
@@ -899,6 +958,7 @@ export const V010_SLOTS_TOOLS: McpToolDef[] = [
       },
       required: ["label", "text"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_slot_replace",
@@ -911,6 +971,7 @@ export const V010_SLOTS_TOOLS: McpToolDef[] = [
       },
       required: ["label", "content"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: false },
   },
   {
     name: "memory_slot_delete",
@@ -922,6 +983,7 @@ export const V010_SLOTS_TOOLS: McpToolDef[] = [
       },
       required: ["label"],
     },
+    annotations: { readOnlyHint: false, destructiveHint: true },
   },
 ];
 
diff --git a/test/mcp-tool-annotations.test.ts b/test/mcp-tool-annotations.test.ts
new file mode 100644
index 000000000..d8a778f75
--- /dev/null
+++ b/test/mcp-tool-annotations.test.ts
@@ -0,0 +1,199 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+
+vi.mock("../src/logger.js", () => ({
+  logger: { info: vi.fn(), warn: vi.fn(), error: vi.fn() },
+}));
+
+vi.mock("node:fs", () => ({
+  existsSync: vi.fn().mockReturnValue(false),
+  readFileSync: vi.fn(),
+  writeFileSync: vi.fn(),
+  mkdirSync: vi.fn(),
+}));
+
+vi.mock("../src/mcp/transport.js", () => ({
+  createStdioTransport: vi.fn(() => ({ start: vi.fn(), stop: vi.fn() })),
+}));
+
+vi.mock("../src/config.js", () => ({
+  getStandalonePersistPath: vi.fn(() => "/tmp/test-annotations.json"),
+}));
+
+import {
+  getAllTools,
+  getVisibleTools,
+  ESSENTIAL_TOOLS,
+  type McpToolDef,
+} from "../src/mcp/tools-registry.js";
+import { handleToolsList } from "../src/mcp/standalone.js";
+import {
+  resetHandleForTests,
+  setLivezProbe,
+} from "../src/mcp/rest-proxy.js";
+
+const READ_ONLY_TOOLS = new Set([
+  "memory_recall",
+  "memory_file_history",
+  "memory_patterns",
+  "memory_sessions",
+  "memory_smart_search",
+  "memory_vision_search",
+  "memory_timeline",
+  "memory_export",
+  "memory_relations",
+  "memory_commit_lookup",
+  "memory_commits",
+  "memory_graph_query",
+  "memory_team_feed",
+  "memory_audit",
+  "memory_frontier",
+  "memory_next",
+  "memory_diagnose",
+  "memory_facet_query",
+  "memory_verify",
+  "memory_lesson_recall",
+  "memory_insight_list",
+  "memory_slot_list",
+  "memory_slot_get",
+]);
+
+const DESTRUCTIVE_TOOLS = new Set([
+  "memory_governance_delete",
+  "memory_heal",
+  "memory_slot_delete",
+]);
+
+const TOTAL = getAllTools().length;
+
+const instantLocalFallbackProbe = vi.fn(async () => ({
+  ok: false,
+  status: 0,
+  statusText: "stubbed: forced local fallback",
+}));
+
+const fetchTrap = vi.fn(async (url: unknown) => {
+  throw new Error(
+    `unexpected real fetch() in mcp-tool-annotations.test.ts: ${String(url)}`,
+  );
+});
+
+function classification(tool: McpToolDef): string {
+  const ro = tool.annotations?.readOnlyHint === true;
+  const de = tool.annotations?.destructiveHint === true;
+  if (ro && !de) return "read-only";
+  if (!ro && de) return "destructive";
+  if (!ro && !de) return "state-changing";
+  return "invalid";
+}
+
+describe("MCP tool risk annotations", () => {
+  it("every tool carries an annotations object", () => {
+    for (const tool of getAllTools()) {
+      expect(tool.annotations, `tool ${tool.name} missing annotations`).toBeDefined();
+      expect(typeof tool.annotations).toBe("object");
+    }
+  });
+
+  it("no tool is both read-only and destructive", () => {
+    for (const tool of getAllTools()) {
+      const a = tool.annotations;
+      if (a?.readOnlyHint && a?.destructiveHint) {
+        throw new Error(`tool ${tool.name} is both readOnly and destructive`);
+      }
+    }
+  });
+
+  it("read-only set is exactly 23 tools with readOnlyHint true + destructiveHint false", () => {
+    const tools = getAllTools();
+    const ro = tools.filter((t) => classification(t) === "read-only");
+    expect(new Set(ro.map((t) => t.name))).toEqual(READ_ONLY_TOOLS);
+    expect(ro.length).toBe(23);
+    for (const t of ro) {
+      expect(t.annotations?.readOnlyHint).toBe(true);
+      expect(t.annotations?.destructiveHint).toBe(false);
+    }
+  });
+
+  it("destructive set is exactly 3 tools with destructiveHint true + readOnlyHint false", () => {
+    const tools = getAllTools();
+    const de = tools.filter((t) => classification(t) === "destructive");
+    expect(new Set(de.map((t) => t.name))).toEqual(DESTRUCTIVE_TOOLS);
+    expect(de.length).toBe(3);
+    for (const t of de) {
+      expect(t.annotations?.destructiveHint).toBe(true);
+      expect(t.annotations?.readOnlyHint).toBe(false);
+    }
+  });
+
+  it("remaining 27 tools are state-changing (readOnlyHint false, destructiveHint false)", () => {
+    const tools = getAllTools();
+    const sc = tools.filter((t) => classification(t) === "state-changing");
+    expect(sc.length).toBe(27);
+    for (const t of sc) {
+      expect(t.annotations?.readOnlyHint).toBe(false);
+      expect(t.annotations?.destructiveHint).toBe(false);
+      expect(READ_ONLY_TOOLS.has(t.name)).toBe(false);
+      expect(DESTRUCTIVE_TOOLS.has(t.name)).toBe(false);
+    }
+  });
+
+  it("every tool falls into exactly one classification (23 + 3 + 27 covers total)", () => {
+    const tools = getAllTools();
+    expect(tools.length).toBe(TOTAL);
+    const counts = { "read-only": 0, destructive: 0, "state-changing": 0, invalid: 0 };
+    for (const t of tools) counts[classification(t) as keyof typeof counts]++;
+    expect(counts["read-only"]).toBe(23);
+    expect(counts.destructive).toBe(3);
+    expect(counts["state-changing"]).toBe(27);
+    expect(counts.invalid).toBe(0);
+    expect(counts["read-only"] + counts.destructive + counts["state-changing"]).toBe(TOTAL);
+  });
+
+  it("getVisibleTools preserves annotations in every visibility mode", () => {
+    const prev = process.env["AGENTMEMORY_TOOLS"];
+    try {
+      for (const mode of ["all", "core"]) {
+        process.env["AGENTMEMORY_TOOLS"] = mode;
+        const visible = getVisibleTools();
+        if (mode === "all") expect(visible.length).toBe(TOTAL);
+        if (mode === "core") expect(visible.length).toBe(ESSENTIAL_TOOLS.size);
+        for (const tool of visible) {
+          expect(tool.annotations, `tool ${tool.name} lost annotations in ${mode} mode`).toBeDefined();
+        }
+      }
+    } finally {
+      if (prev === undefined) delete process.env["AGENTMEMORY_TOOLS"];
+      else process.env["AGENTMEMORY_TOOLS"] = prev;
+    }
+  });
+});
+
+describe("MCP tools/list wire response carries annotations", () => {
+  const originalFetch = globalThis.fetch;
+
+  beforeEach(() => {
+    instantLocalFallbackProbe.mockClear();
+    fetchTrap.mockClear();
+    resetHandleForTests();
+    setLivezProbe(instantLocalFallbackProbe);
+    (globalThis as { fetch: typeof fetch }).fetch =
+      fetchTrap as unknown as typeof fetch;
+  });
+
+  afterEach(() => {
+    (globalThis as { fetch: typeof fetch }).fetch = originalFetch;
+    resetHandleForTests();
+  });
+
+  it("handleToolsList returns tools whose annotations match the registry", async () => {
+    const registry = new Map(getAllTools().map((t) => [t.name, t]));
+    const res = await handleToolsList();
+    expect(Array.isArray(res.tools)).toBe(true);
+    expect(res.tools.length).toBeGreaterThan(0);
+    for (const wire of res.tools as McpToolDef[]) {
+      const reg = registry.get(wire.name);
+      expect(reg, `wire tool ${wire.name} not in registry`).toBeDefined();
+      expect(wire.annotations).toEqual(reg?.annotations);
+    }
+  });
+});