fix: call-actor output length (#317)

Author: MQ37

src/const.ts

@@ -9,12 +9,12 @@ export const ACTOR_MAX_MEMORY_MBYTES = 4_096; // If the Actor requires 8GB of me
 
 // Tool output
 /**
- * Usual tool output limit is 25k tokens, let's use 20k
- * just in case where 1 token =~ 4 characters thus 80k chars.
+ * Usual tool output limit is 25k tokens where 1 token =~ 4 characters
+ * thus 50k chars so we have some buffer becase there was some issue with Claude code Actor call output token count.
  * This is primarily used for Actor tool call output, but we can then
  * reuse this in other tools as well.
  */
-export const TOOL_MAX_OUTPUT_CHARS = 80000;
+export const TOOL_MAX_OUTPUT_CHARS = 50000;
 
 // MCP Server
 export const SERVER_NAME = 'apify-mcp-server';

src/utils/actor.ts

@@ -75,7 +75,7 @@ export function ensureOutputWithinCharLimit(items: DatasetItem[], importantField
      * If important fields are defined, use only those fields for that fallback step.
      */
     let sourceItems = items;
-    // Try only the important fields
+    // Try keeping only the important fields
     if (importantFields.length > 0) {
         const importantItems = items.map((item) => getValuesByDotKeys(item, importantFields));
         const importantItemsString = JSON.stringify(importantItems);

tests/unit/utils.actor.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest';
 
-import { getActorDefinitionStorageFieldNames } from '../../src/utils/actor.js';
+import { ensureOutputWithinCharLimit, getActorDefinitionStorageFieldNames } from '../../src/utils/actor.js';
 
 describe('getActorDefinitionStorageFieldNames', () => {
     it('should return an array of field names from a single view (display.properties and transformation.fields)', () => {
@@ -98,3 +98,40 @@ describe('getActorDefinitionStorageFieldNames', () => {
         expect(result.sort()).toEqual(['bar', 'baz', 'foo']);
     });
 });
+
+describe('ensureOutputWithinCharLimit', () => {
+    it('should return all items when limit is high', () => {
+        const items = [
+            { id: 1, name: 'Item 1', value: 'test' },
+            { id: 2, name: 'Item 2', value: 'test' },
+        ];
+        const charLimit = JSON.stringify(items).length;
+        const result = ensureOutputWithinCharLimit(items, [], charLimit);
+        expect(result).toEqual(items);
+    });
+
+    it('should use important fields when all items exceed limit', () => {
+        const items = [
+            { id: 1, name: 'Item 1', description: 'Very long description that makes this item exceed the limit', extra: 'unnecessary data' },
+            { id: 2, name: 'Item 2', description: 'Another long description', extra: 'more unnecessary data' },
+        ];
+        const importantFields = ['id', 'name'];
+        const charLimit = 100; // Very small limit
+        const result = ensureOutputWithinCharLimit(items, importantFields, charLimit);
+        expect(result).toEqual([
+            { id: 1, name: 'Item 1' },
+            { id: 2, name: 'Item 2' },
+        ]);
+    });
+
+    it('should remove all items when limit is extremely small', () => {
+        const items = [
+            { id: 1, name: 'Item 1' },
+            { id: 2, name: 'Item 2' },
+        ];
+        const charLimit = 10; // Extremely small limit - even empty array JSON "[]" is 2 chars
+        const result = ensureOutputWithinCharLimit(items, [], charLimit);
+        expect(result).toEqual([]);
+        expect(JSON.stringify(result).length).toBeLessThanOrEqual(charLimit);
+    });
+});