diff --git a/src/tools/console.ts b/src/tools/console.ts
index 13630ff..59b2c9d 100644
--- a/src/tools/console.ts
+++ b/src/tools/console.ts
@@ -12,7 +12,7 @@ import {
   truncationFooter,
 } from '../utils/response-helpers.js';
 import { saveOutput } from '../utils/save-output.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 export const listConsoleMessagesTool = {
@@ -63,7 +63,7 @@ export const listConsoleMessagesTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 export const clearConsoleMessagesTool = {
   name: 'clear_console_messages',
@@ -75,7 +75,7 @@ export const clearConsoleMessagesTool = {
     type: 'object',
     properties: {},
   },
-};
+} satisfies ToolDefinition;
 
 const DEFAULT_LIMIT = 50;
 
diff --git a/src/tools/debugging.ts b/src/tools/debugging.ts
index 8cba07c..62e03e3 100644
--- a/src/tools/debugging.ts
+++ b/src/tools/debugging.ts
@@ -1,7 +1,7 @@
 import { successResponse, errorResponse } from '../utils/response-helpers.js';
 import { compareVersions } from '../utils/version.js';
 import { remoteValueToNative } from '../utils/remote-value.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 const MIN_VERSION = '153';
@@ -34,7 +34,7 @@ export const enableDebuggerTool = {
     readOnlyHint: false,
   },
   inputSchema: { type: 'object', properties: {} },
-};
+} satisfies ToolDefinition;
 
 export const listScriptsTool = {
   name: 'list_scripts',
@@ -44,7 +44,7 @@ export const listScriptsTool = {
     readOnlyHint: true,
   },
   inputSchema: { type: 'object', properties: {} },
-};
+} satisfies ToolDefinition;
 
 export const getScriptSourceTool = {
   name: 'get_script_source',
@@ -60,7 +60,7 @@ export const getScriptSourceTool = {
     },
     required: ['scriptUrl'],
   },
-};
+} satisfies ToolDefinition;
 
 export const setLogpointTool = {
   name: 'set_logpoint',
@@ -81,7 +81,7 @@ export const setLogpointTool = {
     },
     required: ['url', 'line', 'expression'],
   },
-};
+} satisfies ToolDefinition;
 
 export const removeLogpointTool = {
   name: 'remove_logpoint',
@@ -96,7 +96,7 @@ export const removeLogpointTool = {
     },
     required: ['logpoint'],
   },
-};
+} satisfies ToolDefinition;
 
 export const getLogpointResultsTool = {
   name: 'get_logpoint_results',
@@ -111,7 +111,7 @@ export const getLogpointResultsTool = {
     },
     required: ['logpoint'],
   },
-};
+} satisfies ToolDefinition;
 
 // ============================================================================
 // Handlers
diff --git a/src/tools/downloads.ts b/src/tools/downloads.ts
index f3203ed..e8ab702 100644
--- a/src/tools/downloads.ts
+++ b/src/tools/downloads.ts
@@ -4,7 +4,7 @@
  */
 
 import { successResponse, errorResponse, jsonResponse } from '../utils/response-helpers.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 // Tool definitions
@@ -15,7 +15,7 @@ export const listDownloadsTool = {
     readOnlyHint: true,
   },
   inputSchema: {
-    type: 'object' as const,
+    type: 'object',
     properties: {
       status: {
         type: 'string',
@@ -37,23 +37,23 @@ export const listDownloadsTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 export const clearDownloadsTool = {
   name: 'clear_downloads',
   description: 'Clear the tracked downloads buffer.',
   inputSchema: {
-    type: 'object' as const,
+    type: 'object',
     properties: {},
   },
-};
+} satisfies ToolDefinition;
 
 export const setDownloadBehaviorTool = {
   name: 'set_download_behavior',
   description:
     'Control how downloads are handled: allow (save silently to the default download directory), deny (cancel), or reset to default. Avoids the native save-file dialog. Requires a recent Firefox.',
   inputSchema: {
-    type: 'object' as const,
+    type: 'object',
     properties: {
       behavior: {
         type: 'string',
@@ -64,7 +64,7 @@ export const setDownloadBehaviorTool = {
     },
     required: ['behavior'],
   },
-};
+} satisfies ToolDefinition;
 
 // Tool handlers
 export async function handleListDownloads(args: unknown): Promise<McpToolResponse> {
diff --git a/src/tools/firefox-management.ts b/src/tools/firefox-management.ts
index 5950fec..e8310db 100644
--- a/src/tools/firefox-management.ts
+++ b/src/tools/firefox-management.ts
@@ -5,7 +5,7 @@
 
 import { readFileSync, existsSync, statSync } from 'node:fs';
 import { errorResponse, successResponse } from '../utils/response-helpers.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 
 // ============================================================================
 // Tool: get_firefox_logs
@@ -35,7 +35,7 @@ export const getFirefoxLogsTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 export async function handleGetFirefoxLogs(input: unknown) {
   try {
@@ -121,7 +121,7 @@ export const getFirefoxInfoTool = {
     type: 'object',
     properties: {},
   },
-};
+} satisfies ToolDefinition;
 
 export async function handleGetFirefoxInfo(_input: unknown) {
   try {
@@ -239,7 +239,7 @@ export const restartFirefoxTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 export async function handleRestartFirefox(input: unknown) {
   try {
diff --git a/src/tools/firefox-prefs.ts b/src/tools/firefox-prefs.ts
index 2787e64..e541290 100644
--- a/src/tools/firefox-prefs.ts
+++ b/src/tools/firefox-prefs.ts
@@ -6,7 +6,7 @@
 
 import { successResponse, errorResponse } from '../utils/response-helpers.js';
 import { generatePrefScript } from '../firefox/pref-utils.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 // ============================================================================
@@ -34,7 +34,7 @@ export const setFirefoxPrefsTool = {
     },
     required: ['prefs'],
   },
-};
+} satisfies ToolDefinition;
 
 export async function handleSetFirefoxPrefs(args: unknown): Promise<McpToolResponse> {
   try {
@@ -145,7 +145,7 @@ export const getFirefoxPrefsTool = {
     },
     required: ['names'],
   },
-};
+} satisfies ToolDefinition;
 
 export async function handleGetFirefoxPrefs(args: unknown): Promise<McpToolResponse> {
   try {
diff --git a/src/tools/input.ts b/src/tools/input.ts
index 37ff43e..1e235c5 100644
--- a/src/tools/input.ts
+++ b/src/tools/input.ts
@@ -5,7 +5,7 @@
 
 import { successResponse, errorResponse } from '../utils/response-helpers.js';
 import { handleUidError } from '../utils/uid-helpers.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 // Tool definitions
@@ -29,7 +29,7 @@ export const clickByUidTool = {
     },
     required: ['uid'],
   },
-};
+} satisfies ToolDefinition;
 
 export const hoverByUidTool = {
   name: 'hover_by_uid',
@@ -47,7 +47,7 @@ export const hoverByUidTool = {
     },
     required: ['uid'],
   },
-};
+} satisfies ToolDefinition;
 
 export const fillByUidTool = {
   name: 'fill_by_uid',
@@ -69,7 +69,7 @@ export const fillByUidTool = {
     },
     required: ['uid', 'value'],
   },
-};
+} satisfies ToolDefinition;
 
 export const dragByUidToUidTool = {
   name: 'drag_by_uid_to_uid',
@@ -91,7 +91,7 @@ export const dragByUidToUidTool = {
     },
     required: ['fromUid', 'toUid'],
   },
-};
+} satisfies ToolDefinition;
 
 export const fillFormByUidTool = {
   name: 'fill_form_by_uid',
@@ -123,7 +123,7 @@ export const fillFormByUidTool = {
     },
     required: ['elements'],
   },
-};
+} satisfies ToolDefinition;
 
 export const uploadFileByUidTool = {
   name: 'upload_file_by_uid',
@@ -145,7 +145,7 @@ export const uploadFileByUidTool = {
     },
     required: ['uid', 'filePath'],
   },
-};
+} satisfies ToolDefinition;
 
 // Handlers
 export async function handleClickByUid(args: unknown): Promise<McpToolResponse> {
diff --git a/src/tools/module.ts b/src/tools/module.ts
index 910b8cc..4811af3 100644
--- a/src/tools/module.ts
+++ b/src/tools/module.ts
@@ -8,11 +8,31 @@
 
 import type { McpToolResponse } from '../types/common.js';
 
+export type JsonSchemaType = 'array' | 'boolean' | 'integer' | 'number' | 'object' | 'string';
+
+export interface JsonSchemaProperty {
+  type: JsonSchemaType | readonly JsonSchemaType[];
+  description?: string;
+  enum?: readonly string[];
+  /** Schema of array elements (when type is 'array'). */
+  items?: JsonSchemaProperty;
+  /** Schema for values of an open-key object (prefs-style maps). */
+  additionalProperties?: { oneOf: Array<{ type: JsonSchemaType }> };
+  properties?: Record<string, JsonSchemaProperty>;
+  required?: readonly string[];
+}
+
+export interface InputSchema {
+  type: 'object';
+  properties: Record<string, JsonSchemaProperty>;
+  required?: readonly string[];
+}
+
 export interface ToolDefinition {
   name: string;
   description: string;
   annotations?: { readOnlyHint?: boolean; [key: string]: unknown };
-  inputSchema: Record<string, unknown>;
+  inputSchema: InputSchema;
 }
 
 export type ToolHandler = (input: unknown) => Promise<McpToolResponse>;
diff --git a/src/tools/network.ts b/src/tools/network.ts
index 12841fc..aed6318 100644
--- a/src/tools/network.ts
+++ b/src/tools/network.ts
@@ -14,7 +14,7 @@ import {
   TOKEN_LIMITS,
 } from '../utils/response-helpers.js';
 import { saveOutput } from '../utils/save-output.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 import type { NetworkBodyResult } from '../firefox/events/network.js';
 
@@ -27,7 +27,7 @@ export const listNetworkRequestsTool = {
     readOnlyHint: true,
   },
   inputSchema: {
-    type: 'object' as const,
+    type: 'object',
     properties: {
       limit: {
         type: 'number',
@@ -92,7 +92,7 @@ export const listNetworkRequestsTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 export const getNetworkRequestTool = {
   name: 'get_network_request',
@@ -102,7 +102,7 @@ export const getNetworkRequestTool = {
     readOnlyHint: true,
   },
   inputSchema: {
-    type: 'object' as const,
+    type: 'object',
     properties: {
       id: {
         type: 'string',
@@ -129,7 +129,7 @@ export const getNetworkRequestTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 /**
  * Fetch a body without letting a missing facade method or transport error fail
diff --git a/src/tools/pages.ts b/src/tools/pages.ts
index ebc4b4d..2ece6e1 100644
--- a/src/tools/pages.ts
+++ b/src/tools/pages.ts
@@ -9,8 +9,8 @@ import {
   truncationFooter,
 } from '../utils/response-helpers.js';
 import { saveOutput } from '../utils/save-output.js';
-import { defineModule } from './module.js';
 import { READINESS_STATES, isReadinessState, type ReadinessState } from '../firefox/pages.js';
+import { defineModule, type JsonSchemaProperty, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 const DEFAULT_MAX_CONTENT_CHARS = 20_000;
@@ -25,7 +25,7 @@ const waitSchema = {
   type: 'string',
   enum: [...READINESS_STATES],
   description: WAIT_DESCRIPTION,
-};
+} satisfies JsonSchemaProperty;
 
 /**
  * Validate the optional `wait` argument.
@@ -61,7 +61,7 @@ export const listPagesTool = {
     type: 'object',
     properties: {},
   },
-};
+} satisfies ToolDefinition;
 
 export const newPageTool = {
   name: 'new_page',
@@ -80,7 +80,7 @@ export const newPageTool = {
     },
     required: ['url'],
   },
-};
+} satisfies ToolDefinition;
 
 export const navigatePageTool = {
   name: 'navigate_page',
@@ -99,7 +99,7 @@ export const navigatePageTool = {
     },
     required: ['url'],
   },
-};
+} satisfies ToolDefinition;
 
 export const selectPageTool = {
   name: 'select_page',
@@ -125,7 +125,7 @@ export const selectPageTool = {
     },
     required: [],
   },
-};
+} satisfies ToolDefinition;
 
 export const closePageTool = {
   name: 'close_page',
@@ -143,7 +143,7 @@ export const closePageTool = {
     },
     required: ['pageIdx'],
   },
-};
+} satisfies ToolDefinition;
 
 export const getPageTextTool = {
   name: 'get_page_text',
@@ -153,7 +153,7 @@ export const getPageTextTool = {
     readOnlyHint: true,
   },
   inputSchema: {
-    type: 'object' as const,
+    type: 'object',
     properties: {
       maxLength: {
         type: 'number',
@@ -172,7 +172,7 @@ export const getPageTextTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 /**
  * Format page list compactly
diff --git a/src/tools/privileged-context.ts b/src/tools/privileged-context.ts
index 5ad1c02..325f8e0 100644
--- a/src/tools/privileged-context.ts
+++ b/src/tools/privileged-context.ts
@@ -7,7 +7,7 @@ import { successResponse, errorResponse, previewExcerpt } from '../utils/respons
 import { validateFunction } from '../utils/js-validation.js';
 import { remoteValueToNative } from '../utils/remote-value.js';
 import { saveOutput } from '../utils/save-output.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 // list_extensions lives with the other extension tools in webextension.ts, but
 // it needs parent access (AddonManager), so it is registered here under the
 // privileged module rather than the unprivileged webextension module.
@@ -25,7 +25,7 @@ export const listPrivilegedContextsTool = {
     type: 'object',
     properties: {},
   },
-};
+} satisfies ToolDefinition;
 
 export const selectPrivilegedContextTool = {
   name: 'select_privileged_context',
@@ -44,7 +44,7 @@ export const selectPrivilegedContextTool = {
     },
     required: ['contextId'],
   },
-};
+} satisfies ToolDefinition;
 
 export const evaluatePrivilegedScriptTool = {
   name: 'evaluate_privileged_script',
@@ -77,7 +77,7 @@ export const evaluatePrivilegedScriptTool = {
     },
     required: ['function', 'context'],
   },
-};
+} satisfies ToolDefinition;
 
 function formatContextList(contexts: any[]): string {
   if (contexts.length === 0) {
diff --git a/src/tools/profiler.ts b/src/tools/profiler.ts
index 5992edd..986efcf 100644
--- a/src/tools/profiler.ts
+++ b/src/tools/profiler.ts
@@ -1,7 +1,7 @@
 import { successResponse, errorResponse } from '../utils/response-helpers.js';
 import { compareVersions } from '../utils/version.js';
 import type { FirefoxDevTools } from '../firefox/index.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 const MIN_FIREFOX_VERSION = '154.0';
@@ -40,7 +40,7 @@ export const profilerIsActiveTool = {
     type: 'object',
     properties: {},
   },
-};
+} satisfies ToolDefinition;
 
 export async function handleProfilerIsActive(_args: unknown): Promise<McpToolResponse> {
   try {
@@ -101,7 +101,7 @@ export const profilerStartTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 export async function handleProfilerStart(args: unknown): Promise<McpToolResponse> {
   try {
@@ -172,7 +172,7 @@ export const profilerStopTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 export async function handleProfilerStop(args: unknown): Promise<McpToolResponse> {
   try {
diff --git a/src/tools/screencast.ts b/src/tools/screencast.ts
index cc28921..dd83eac 100644
--- a/src/tools/screencast.ts
+++ b/src/tools/screencast.ts
@@ -1,7 +1,7 @@
 import { successResponse, errorResponse } from '../utils/response-helpers.js';
 import { compareVersions } from '../utils/version.js';
 import type { FirefoxDevTools } from '../firefox/index.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 const MIN_FIREFOX_VERSION = '154.0';
@@ -60,7 +60,7 @@ export const screencastStartTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 export async function handleScreencastStart(args: unknown): Promise<McpToolResponse> {
   try {
@@ -134,7 +134,7 @@ export const screencastStopTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 export async function handleScreencastStop(args: unknown): Promise<McpToolResponse> {
   try {
diff --git a/src/tools/screenshot.ts b/src/tools/screenshot.ts
index 1e1bac9..1705ad8 100644
--- a/src/tools/screenshot.ts
+++ b/src/tools/screenshot.ts
@@ -5,7 +5,7 @@
 import { successResponse, errorResponse } from '../utils/response-helpers.js';
 import { handleUidError } from '../utils/uid-helpers.js';
 import { saveOutput } from '../utils/save-output.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 const SAVE_TO_SCHEMA = {
@@ -27,7 +27,7 @@ export const screenshotPageTool = {
       saveTo: SAVE_TO_SCHEMA,
     },
   },
-};
+} satisfies ToolDefinition;
 
 export const screenshotByUidTool = {
   name: 'screenshot_by_uid',
@@ -46,7 +46,7 @@ export const screenshotByUidTool = {
     },
     required: ['uid'],
   },
-};
+} satisfies ToolDefinition;
 
 /**
  * Save screenshot to file and return text response with path.
diff --git a/src/tools/script.ts b/src/tools/script.ts
index 0c4bac3..686eb1c 100644
--- a/src/tools/script.ts
+++ b/src/tools/script.ts
@@ -6,7 +6,7 @@ import { successResponse, errorResponse, previewExcerpt } from '../utils/respons
 import { remoteValueToNative } from '../utils/remote-value.js';
 import { validateFunction } from '../utils/js-validation.js';
 import { saveOutput } from '../utils/save-output.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 export const evaluateScriptTool = {
@@ -59,7 +59,7 @@ export const evaluateScriptTool = {
     },
     required: ['function'],
   },
-};
+} satisfies ToolDefinition;
 
 // Constants
 const DEFAULT_TIMEOUT = 5000; // 5 seconds
diff --git a/src/tools/snapshot.ts b/src/tools/snapshot.ts
index 00f2b47..8903e1c7 100644
--- a/src/tools/snapshot.ts
+++ b/src/tools/snapshot.ts
@@ -11,7 +11,7 @@ import {
 } from '../utils/response-helpers.js';
 import { handleUidError } from '../utils/uid-helpers.js';
 import { saveOutput } from '../utils/save-output.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 const DEFAULT_SNAPSHOT_LINES = 100;
@@ -64,7 +64,7 @@ export const takeSnapshotTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 export const resolveUidToSelectorTool = {
   name: 'resolve_uid_to_selector',
@@ -82,7 +82,7 @@ export const resolveUidToSelectorTool = {
     },
     required: ['uid'],
   },
-};
+} satisfies ToolDefinition;
 
 export const clearSnapshotTool = {
   name: 'clear_snapshot',
@@ -94,7 +94,7 @@ export const clearSnapshotTool = {
     type: 'object',
     properties: {},
   },
-};
+} satisfies ToolDefinition;
 
 // Handlers
 export async function handleTakeSnapshot(args: unknown): Promise<McpToolResponse> {
diff --git a/src/tools/utilities.ts b/src/tools/utilities.ts
index c592259..bb34439 100644
--- a/src/tools/utilities.ts
+++ b/src/tools/utilities.ts
@@ -3,7 +3,7 @@
  */
 
 import { successResponse, errorResponse } from '../utils/response-helpers.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 // Tool definitions - Dialogs
@@ -22,7 +22,7 @@ export const acceptDialogTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 export const dismissDialogTool = {
   name: 'dismiss_dialog',
@@ -34,7 +34,7 @@ export const dismissDialogTool = {
     type: 'object',
     properties: {},
   },
-};
+} satisfies ToolDefinition;
 
 // Tool definitions - History
 export const navigateHistoryTool = {
@@ -54,7 +54,7 @@ export const navigateHistoryTool = {
     },
     required: ['direction'],
   },
-};
+} satisfies ToolDefinition;
 
 // Tool definitions - Viewport
 export const setViewportSizeTool = {
@@ -77,7 +77,7 @@ export const setViewportSizeTool = {
     },
     required: ['width', 'height'],
   },
-};
+} satisfies ToolDefinition;
 
 // Handlers - Dialogs
 export async function handleAcceptDialog(args: unknown): Promise<McpToolResponse> {
diff --git a/src/tools/webextension.ts b/src/tools/webextension.ts
index d22f961..f68c3a8 100644
--- a/src/tools/webextension.ts
+++ b/src/tools/webextension.ts
@@ -10,7 +10,7 @@
  */
 
 import { successResponse, errorResponse } from '../utils/response-helpers.js';
-import { defineModule } from './module.js';
+import { defineModule, type ToolDefinition } from './module.js';
 import type { McpToolResponse } from '../types/common.js';
 
 // ============================================================================
@@ -49,7 +49,7 @@ export const installExtensionTool = {
     },
     required: ['type'],
   },
-};
+} satisfies ToolDefinition;
 
 export async function handleInstallExtension(args: unknown): Promise<McpToolResponse> {
   try {
@@ -124,7 +124,7 @@ export const uninstallExtensionTool = {
     },
     required: ['id'],
   },
-};
+} satisfies ToolDefinition;
 
 export async function handleUninstallExtension(args: unknown): Promise<McpToolResponse> {
   try {
@@ -182,7 +182,7 @@ export const listExtensionsTool = {
       },
     },
   },
-};
+} satisfies ToolDefinition;
 
 interface ExtensionInfo {
   id: string;