Truncate tool output and limit tool response.

Also limit number of Actors used to avoid rate limiting.

Author: jirispilka

README.md

@@ -43,14 +43,9 @@ Any [Apify Actor](https://apify.com/store) can be used as a tool.
 By default, the server is pre-configured with the Actors specified below, but it can be overridden by providing a list of Actor names in the `actors` query parameter.
 
 ```text
-   'apidojo/tweet-scraper',
-   'apify/facebook-posts-scraper',
-   'apify/google-search-scraper',
    'apify/instagram-scraper',
    'apify/rag-web-browser',
-   'clockworks/free-tiktok-scraper',
    'lukaskrivka/google-maps-with-contact-details',
-   'voyager/booking-scraper'
 ```
 The MCP server loads the Actor input schema and creates MCP tools corresponding to the Actors.
 See this example of input schema for the [RAG Web Browser](https://apify.com/apify/rag-web-browser/input-schema).

src/const.ts

@@ -3,18 +3,16 @@ export const SERVER_VERSION = '0.1.0';
 
 export const defaults = {
     actors: [
-        'apidojo/tweet-scraper',
-        'apify/facebook-posts-scraper',
-        'apify/google-search-scraper',
         'apify/instagram-scraper',
         'apify/rag-web-browser',
-        'clockworks/free-tiktok-scraper',
-        'compass/crawler-google-places',
         'lukaskrivka/google-maps-with-contact-details',
-        'voyager/booking-scraper',
     ],
 };
 
+export const ACTOR_OUTPUT_MAX_CHARS_PER_ITEM = 1_000;
+export const ACTOR_OUTPUT_TRUNCATED_MESSAGE = `Output was truncated because it will not fit into context.` +
+    `There is no reason to call this tool again!`;
+
 export enum Routes {
     ROOT = '/',
     SSE = '/sse',

src/examples/clientStdioChat.ts

@@ -121,7 +121,7 @@ class MCPClient {
             results = await this.client.callTool(params, CallToolResultSchema, { timeout: REQUEST_TIMEOUT });
             if (results.content instanceof Array && results.content.length !== 0) {
                 const text = results.content.map((x) => x.text);
-                messages.push({ role: 'user', content: text.join('\n\n') });
+                messages.push({ role: 'user', content: `Tool result: ${text.join('\n\n')}` });
             } else {
                 messages.push({ role: 'user', content: `No results retrieved from ${params.name}` });
             }

src/server.ts

@@ -9,7 +9,13 @@ import { Actor } from 'apify';
 import { ApifyClient } from 'apify-client';
 
 import { getActorsAsTools } from './actorDefinition.js';
-import { defaults, SERVER_NAME, SERVER_VERSION } from './const.js';
+import {
+    ACTOR_OUTPUT_MAX_CHARS_PER_ITEM,
+    ACTOR_OUTPUT_TRUNCATED_MESSAGE,
+    defaults,
+    SERVER_NAME,
+    SERVER_VERSION
+} from './const.js';
 import { log } from './logger.js';
 import type { Tool } from './types';
 
@@ -123,14 +129,20 @@ export class ApifyMcpServer {
 
             try {
                 const items = await this.callActorGetDataset(tool.actorName, args);
-                return { content: items.map((item) => ({ type: 'text', text: JSON.stringify(item) })) };
+                const content = items.map(item => {
+                    let text = JSON.stringify(item).slice(0, ACTOR_OUTPUT_MAX_CHARS_PER_ITEM);
+                    return text.length === ACTOR_OUTPUT_MAX_CHARS_PER_ITEM
+                        ? { type: 'text', text: `${text} ... ${ACTOR_OUTPUT_TRUNCATED_MESSAGE}` }
+                        : { type: 'text', text };
+                });
+                return { content: content };
+
             } catch (error) {
                 log.error(`Error calling tool: ${error}`);
                 throw new Error(`Error calling tool: ${error}`);
             }
         });
     }
-
     async connect(transport: Transport): Promise<void> {
         await this.server.connect(transport);
     }