Add option to encode structuredContent as TOON

Author: Piotr Paulski

package-lock.json

@@ -54,6 +54,7 @@
     "@rollup/plugin-json": "^6.1.0",
     "@rollup/plugin-node-resolve": "^16.0.3",
     "@stylistic/eslint-plugin": "^5.4.0",
+    "@toon-format/toon": "^2.2.0",
     "@types/debug": "^4.1.12",
     "@types/filesystem": "^0.0.36",
     "@types/node": "^25.0.0",

package.json

@@ -13,7 +13,7 @@ import {SlimMcpResponse} from './SlimMcpResponse.js';
 import {ClearcutLogger} from './telemetry/ClearcutLogger.js';
 import {bucketizeLatency} from './telemetry/transformation.js';
 import type {CallToolResult} from './third_party/index.js';
-import {zod} from './third_party/index.js';
+import {zod, toonEncode} from './third_party/index.js';
 import type {ToolCategory} from './tools/categories.js';
 import {labels, OFF_BY_DEFAULT_CATEGORIES} from './tools/categories.js';
 import type {DefinedPageTool, ToolDefinition} from './tools/ToolDefinition.js';
@@ -267,7 +267,11 @@ export class ToolHandler {
       }
       success = true;
       if (this.serverArgs.experimentalStructuredContent) {
-        result.structuredContent = structuredContent as Record<string, unknown>;
+        if (this.serverArgs.experimentalStructuredContentFormat === 'toon') {
+          result.structuredContent = { format: 'toon', data: toonEncode(structuredContent)};
+        } else {
+          result.structuredContent = structuredContent as Record<string, unknown>;
+        }
       }
       return result;
     } catch (err) {

src/ToolHandler.ts

@@ -169,6 +169,12 @@ export const cliOptions = {
     type: 'boolean',
     describe: 'Whether to output structured formatted content.',
   },
+  experimentalStructuredContentFormat: {
+    type: 'string',
+    describe: 'The format of the structured content. Defaults to "json".',
+    choices: ['toon', 'json'] as const,
+    hidden: true,
+  },
   experimentalIncludeAllPages: {
     type: 'boolean',
     describe:
@@ -293,7 +299,7 @@ export function parseArguments(
   const yargsInstance = yargs(hideBin(argv))
     .scriptName('npx chrome-devtools-mcp@latest')
     .options(cliOptions)
-    .check(args => {
+    .middleware(args => {
       // We can't set default in the options else
       // Yargs will complain
       if (
@@ -310,6 +316,19 @@ export function parseArguments(
         );
         args.usageStatistics = false;
       }
+      if (args.experimentalStructuredContentFormat && args.experimentalStructuredContent === undefined) {
+        args.experimentalStructuredContent = true;
+      }
+      if (args.experimentalStructuredContentFormat === undefined && args.experimentalStructuredContent) {
+        args.experimentalStructuredContentFormat = 'json';
+      }
+    })
+    .check(args => {
+      if (args.experimentalStructuredContentFormat && !args.experimentalStructuredContent) {
+        throw new Error(
+          'The --experimentalStructuredContentFormat option can only be used when --experimentalStructuredContent is enabled.'
+        );
+      }
       return true;
     })
     .example([

src/bin/chrome-devtools-mcp-cli-options.ts

@@ -54,6 +54,7 @@ export {
   Browser as BrowserEnum,
   type ChromeReleaseChannel as BrowsersChromeReleaseChannel,
 } from '@puppeteer/browsers';
+export {encode as toonEncode} from '@toon-format/toon';
 
 import {
   snapshot as snapshotImpl,

src/third_party/index.ts

@@ -907,6 +907,36 @@ IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 
+-------------------- DEPENDENCY DIVIDER --------------------
+
+Name: @toon-format/toon
+URL: https://toonformat.dev
+Version: <VERSION>
+License: MIT
+
+MIT License
+
+Copyright (c) 2025-PRESENT Johann Schopplich
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+
 -------------------- DEPENDENCY DIVIDER --------------------
 
 Name: chrome-devtools-frontend