fix(agent): filter out empty params to ensure LLM can set tool params at runtime

apps/sim/providers/utils.ts

@@ -1011,10 +1011,21 @@ export function prepareToolExecution(
   toolParams: Record<string, any>
   executionParams: Record<string, any>
 } {
+  // Filter out empty/null/undefined values from user params
+  // so that cleared fields don't override LLM-generated values
+  const filteredUserParams: Record<string, any> = {}
+  if (tool.params) {
+    for (const [key, value] of Object.entries(tool.params)) {
+      if (value !== undefined && value !== null && value !== '') {
+        filteredUserParams[key] = value
+      }
+    }
+  }
+
   // User-provided params take precedence over LLM-generated params
   const toolParams = {
     ...llmArgs,
-    ...tool.params,
+    ...filteredUserParams,
   }
 
   // Add system parameters for execution

apps/sim/tools/params.test.ts

@@ -177,6 +177,44 @@ describe('Tool Parameters Utils', () => {
       expect(merged.message).toBe('Hello world')
       expect(merged.timeout).toBe(10000)
     })
+
+    it.concurrent('should skip empty strings so LLM values are used', () => {
+      const userProvided = {
+        apiKey: 'user-key',
+        channel: '', // User cleared this field
+        message: '', // User cleared this field too
+      }
+      const llmGenerated = {
+        message: 'Hello world',
+        channel: '#random',
+        timeout: 10000,
+      }
+
+      const merged = mergeToolParameters(userProvided, llmGenerated)
+
+      expect(merged.apiKey).toBe('user-key') // Non-empty user value preserved
+      expect(merged.channel).toBe('#random') // LLM value used because user value was empty
+      expect(merged.message).toBe('Hello world') // LLM value used because user value was empty
+      expect(merged.timeout).toBe(10000)
+    })
+
+    it.concurrent('should skip null and undefined values', () => {
+      const userProvided = {
+        apiKey: 'user-key',
+        channel: null,
+        message: undefined,
+      }
+      const llmGenerated = {
+        message: 'Hello world',
+        channel: '#random',
+      }
+
+      const merged = mergeToolParameters(userProvided, llmGenerated)
+
+      expect(merged.apiKey).toBe('user-key')
+      expect(merged.channel).toBe('#random') // LLM value used
+      expect(merged.message).toBe('Hello world') // LLM value used
+    })
   })
 
   describe('validateToolParameters', () => {

apps/sim/tools/params.ts

@@ -572,16 +572,27 @@ export function createExecutionToolSchema(toolConfig: ToolConfig): ToolSchema {
 }
 
 /**
- * Merges user-provided parameters with LLM-generated parameters
+ * Merges user-provided parameters with LLM-generated parameters.
+ * User-provided parameters take precedence, but empty strings are skipped
+ * so that LLM-generated values are used when user clears a field.
  */
 export function mergeToolParameters(
   userProvidedParams: Record<string, unknown>,
   llmGeneratedParams: Record<string, unknown>
 ): Record<string, unknown> {
-  // User-provided parameters take precedence
+  // Filter out empty strings from user-provided params
+  // so that cleared fields don't override LLM values
+  const filteredUserParams: Record<string, unknown> = {}
+  for (const [key, value] of Object.entries(userProvidedParams)) {
+    if (value !== undefined && value !== null && value !== '') {
+      filteredUserParams[key] = value
+    }
+  }
+
+  // User-provided parameters take precedence (after filtering empty values)
   return {
     ...llmGeneratedParams,
-    ...userProvidedParams,
+    ...filteredUserParams,
   }
 }