diff --git a/src/tools/ToolDefinition.ts b/src/tools/ToolDefinition.ts
index d017640cd..20c3c2e26 100644
--- a/src/tools/ToolDefinition.ts
+++ b/src/tools/ToolDefinition.ts
@@ -24,6 +24,16 @@ export interface ToolDefinition<
      * If true, the tool does not modify its environment.
      */
     readOnlyHint: boolean;
+    /**
+     * If true, the tool may perform destructive updates to its environment.
+     * If false, the tool performs only additive updates.
+     */
+    destructiveHint?: boolean;
+    /**
+     * If true, this tool may interact with an "open world" of external
+     * entities (e.g., websites, APIs, external services).
+     */
+    openWorldHint?: boolean;
   };
   schema: Schema;
   handler: (
diff --git a/src/tools/console.ts b/src/tools/console.ts
index 9c3d145bb..05d339f08 100644
--- a/src/tools/console.ts
+++ b/src/tools/console.ts
@@ -43,6 +43,7 @@ export const listConsoleMessages = defineTool({
   annotations: {
     category: ToolCategory.DEBUGGING,
     readOnlyHint: true,
+    openWorldHint: true,
   },
   schema: {
     pageSize: zod
@@ -91,6 +92,7 @@ export const getConsoleMessage = defineTool({
   annotations: {
     category: ToolCategory.DEBUGGING,
     readOnlyHint: true,
+    openWorldHint: true,
   },
   schema: {
     msgid: zod
diff --git a/src/tools/emulation.ts b/src/tools/emulation.ts
index 13119250d..cb04befe9 100644
--- a/src/tools/emulation.ts
+++ b/src/tools/emulation.ts
@@ -21,6 +21,7 @@ export const emulate = defineTool({
   annotations: {
     category: ToolCategory.EMULATION,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     networkConditions: zod
diff --git a/src/tools/input.ts b/src/tools/input.ts
index 505568922..a9aea5aca 100644
--- a/src/tools/input.ts
+++ b/src/tools/input.ts
@@ -18,6 +18,7 @@ export const click = defineTool({
   annotations: {
     category: ToolCategory.INPUT,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     uid: zod
@@ -57,6 +58,7 @@ export const hover = defineTool({
   annotations: {
     category: ToolCategory.INPUT,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     uid: zod
@@ -141,6 +143,7 @@ export const fill = defineTool({
   annotations: {
     category: ToolCategory.INPUT,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     uid: zod
@@ -169,6 +172,7 @@ export const drag = defineTool({
   annotations: {
     category: ToolCategory.INPUT,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     from_uid: zod.string().describe('The uid of the element to drag'),
@@ -198,6 +202,7 @@ export const fillForm = defineTool({
   annotations: {
     category: ToolCategory.INPUT,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     elements: zod
@@ -230,6 +235,7 @@ export const uploadFile = defineTool({
   annotations: {
     category: ToolCategory.INPUT,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     uid: zod
@@ -278,6 +284,7 @@ export const pressKey = defineTool({
   annotations: {
     category: ToolCategory.INPUT,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     key: zod
diff --git a/src/tools/network.ts b/src/tools/network.ts
index d3b6c1fe6..3918e4f31 100644
--- a/src/tools/network.ts
+++ b/src/tools/network.ts
@@ -38,6 +38,7 @@ export const listNetworkRequests = defineTool({
   annotations: {
     category: ToolCategory.NETWORK,
     readOnlyHint: true,
+    openWorldHint: true,
   },
   schema: {
     pageSize: zod
@@ -92,6 +93,7 @@ export const getNetworkRequest = defineTool({
   annotations: {
     category: ToolCategory.NETWORK,
     readOnlyHint: true,
+    openWorldHint: true,
   },
   schema: {
     reqid: zod
diff --git a/src/tools/pages.ts b/src/tools/pages.ts
index 96ab2cc01..8975ae9dc 100644
--- a/src/tools/pages.ts
+++ b/src/tools/pages.ts
@@ -16,6 +16,7 @@ export const listPages = defineTool({
   annotations: {
     category: ToolCategory.NAVIGATION,
     readOnlyHint: true,
+    openWorldHint: true,
   },
   schema: {},
   handler: async (_request, response) => {
@@ -29,6 +30,7 @@ export const selectPage = defineTool({
   annotations: {
     category: ToolCategory.NAVIGATION,
     readOnlyHint: true,
+    openWorldHint: true,
   },
   schema: {
     pageIdx: zod
@@ -57,6 +59,7 @@ export const closePage = defineTool({
   annotations: {
     category: ToolCategory.NAVIGATION,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     pageIdx: zod
@@ -85,6 +88,7 @@ export const newPage = defineTool({
   annotations: {
     category: ToolCategory.NAVIGATION,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     url: zod.string().describe('URL to load in a new page.'),
@@ -109,6 +113,7 @@ export const navigatePage = defineTool({
   annotations: {
     category: ToolCategory.NAVIGATION,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     type: zod
@@ -205,6 +210,7 @@ export const resizePage = defineTool({
   annotations: {
     category: ToolCategory.EMULATION,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     width: zod.number().describe('Page width'),
@@ -229,6 +235,7 @@ export const handleDialog = defineTool({
   annotations: {
     category: ToolCategory.INPUT,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     action: zod
diff --git a/src/tools/performance.ts b/src/tools/performance.ts
index a8b24903c..0bbe0d007 100644
--- a/src/tools/performance.ts
+++ b/src/tools/performance.ts
@@ -26,6 +26,7 @@ export const startTrace = defineTool({
   annotations: {
     category: ToolCategory.PERFORMANCE,
     readOnlyHint: true,
+    openWorldHint: true,
   },
   schema: {
     reload: zod
@@ -107,6 +108,7 @@ export const stopTrace = defineTool({
   annotations: {
     category: ToolCategory.PERFORMANCE,
     readOnlyHint: true,
+    openWorldHint: true,
   },
   schema: {},
   handler: async (_request, response, context) => {
@@ -125,6 +127,7 @@ export const analyzeInsight = defineTool({
   annotations: {
     category: ToolCategory.PERFORMANCE,
     readOnlyHint: true,
+    openWorldHint: true,
   },
   schema: {
     insightSetId: zod
diff --git a/src/tools/screenshot.ts b/src/tools/screenshot.ts
index 4312c02aa..ecd94ff33 100644
--- a/src/tools/screenshot.ts
+++ b/src/tools/screenshot.ts
@@ -17,6 +17,7 @@ export const screenshot = defineTool({
     category: ToolCategory.DEBUGGING,
     // Not read-only due to filePath param.
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     format: zod
diff --git a/src/tools/script.ts b/src/tools/script.ts
index de28fe0b4..33d096267 100644
--- a/src/tools/script.ts
+++ b/src/tools/script.ts
@@ -17,6 +17,7 @@ so returned values have to JSON-serializable.`,
   annotations: {
     category: ToolCategory.DEBUGGING,
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     function: zod.string().describe(
diff --git a/src/tools/snapshot.ts b/src/tools/snapshot.ts
index 143d04093..2a24f2e47 100644
--- a/src/tools/snapshot.ts
+++ b/src/tools/snapshot.ts
@@ -18,6 +18,7 @@ in the DevTools Elements panel (if any).`,
     category: ToolCategory.DEBUGGING,
     // Not read-only due to filePath param.
     readOnlyHint: false,
+    openWorldHint: true,
   },
   schema: {
     verbose: zod
@@ -47,6 +48,7 @@ export const waitFor = defineTool({
   annotations: {
     category: ToolCategory.NAVIGATION,
     readOnlyHint: true,
+    openWorldHint: true,
   },
   schema: {
     text: zod.string().describe('Text to appear on the page'),