feat: add experimentalGcfFormat flag for GCF-encoded tool responses

package.json

@@ -55,6 +55,7 @@
     "@rollup/plugin-json": "^6.1.0",
     "@rollup/plugin-node-resolve": "^16.0.3",
     "@stylistic/eslint-plugin": "^5.4.0",
+    "@blackwell-systems/gcf": "2.1.2",
     "@toon-format/toon": "^2.2.0",
     "@types/debug": "^4.1.12",
     "@types/filesystem": "^0.0.36",

src/McpResponse.ts

@@ -17,7 +17,7 @@ import type {McpContext} from './McpContext.js';
 import type {McpPage} from './McpPage.js';
 import {UncaughtError} from './PageCollector.js';
 import {TextSnapshot} from './TextSnapshot.js';
-import {DevTools, toonEncode, type Protocol} from './third_party/index.js';
+import {DevTools, toonEncode, gcfEncode, type Protocol} from './third_party/index.js';
 import type {
   ConsoleMessage,
   ImageContent,
@@ -525,6 +525,7 @@ export class McpResponse implements Response {
     toolName: string,
     context: McpContext,
     useToon = false,
+    useGcf = false,
   ): Promise<{
     content: Array<TextContent | ImageContent>;
     structuredContent: object;
@@ -771,6 +772,7 @@ export class McpResponse implements Response {
         errorMessage: this.#error?.message,
       },
       useToon,
+      useGcf,
     );
   }
 
@@ -792,10 +794,12 @@ export class McpResponse implements Response {
       errorMessage?: string;
     },
     useToon: boolean,
+    useGcf = false,
   ): Promise<{
     content: Array<TextContent | ImageContent>;
     structuredContent: object;
   }> {
+    const compactEncode = useGcf ? gcfEncode : useToon ? toonEncode : null;
     const structuredContent: {
       snapshot?: object;
       snapshotFilePath?: string;
@@ -1057,8 +1061,8 @@ Call ${handleDialog.name} to handle it before continuing.`);
         structuredContent.snapshot = data.snapshot.toJSON();
         response.push('## Latest page snapshot');
         response.push(
-          useToon
-            ? toonEncode(structuredContent.snapshot)
+          compactEncode
+            ? compactEncode(structuredContent.snapshot)
             : data.snapshot.toString(),
         );
       }
@@ -1095,8 +1099,8 @@ Call ${handleDialog.name} to handle it before continuing.`);
 
         structuredContent.heapSnapshotData = formatter.toJSON();
         response.push(
-          useToon
-            ? toonEncode(structuredContent.heapSnapshotData)
+          compactEncode
+            ? compactEncode(structuredContent.heapSnapshotData)
             : formatter.toString(),
         );
       }
@@ -1244,8 +1248,8 @@ Call ${handleDialog.name} to handle it before continuing.`);
             i.toJSON(),
           );
           response.push(
-            ...(useToon
-              ? [toonEncode(structuredContent.networkRequests)]
+            ...(compactEncode
+              ? [compactEncode(structuredContent.networkRequests)]
               : paginationData.items.map(i => i.toString())),
           );
         }
@@ -1269,8 +1273,8 @@ Call ${handleDialog.name} to handle it before continuing.`);
           item.toJSON(),
         );
         response.push(...paginationData.info);
-        if (useToon) {
-          response.push(toonEncode(structuredContent.consoleMessages));
+        if (compactEncode) {
+          response.push(compactEncode(structuredContent.consoleMessages));
         } else {
           response.push(...paginationData.items.map(item => item.toString()));
         }

src/ToolHandler.ts

@@ -263,6 +263,7 @@ export class ToolHandler {
         this.tool.name,
         context,
         this.serverArgs.experimentalToonFormat ?? false,
+        this.serverArgs.experimentalGcfFormat ?? false,
       );
       const result: CallToolResult & {
         structuredContent?: Record<string, unknown>;

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

@@ -176,6 +176,12 @@ export const cliOptions = {
       'Whether to format structured data in text response using Token-Oriented Object Notation. Defaults to false which represents the embedded content as formatted JSON instead.',
     hidden: true,
   },
+  experimentalGcfFormat: {
+    type: 'boolean',
+    describe:
+      'Whether to format structured data in text response using Graph Compact Format. Defaults to false which represents the embedded content as formatted JSON instead.',
+    hidden: true,
+  },
   experimentalIncludeAllPages: {
     type: 'boolean',
     describe:

src/third_party/index.ts

@@ -58,6 +58,7 @@ export {
   type ChromeReleaseChannel as BrowsersChromeReleaseChannel,
 } from '@puppeteer/browsers';
 export {encode as toonEncode} from '@toon-format/toon';
+export {encodeGeneric as gcfEncode} from '@blackwell-systems/gcf';
 
 import {
   snapshot as snapshotImpl,