Fix #4083 JSON parse error when tool does not accept parameters (#4084)

* Fix #4083: JSON parse error when tool does not accept parameters

* Reformat for visual coolness

---------

Co-authored-by: Cohee <18619528+Cohee1207@users.noreply.github.com>

public/scripts/tool-calling.js

@@ -297,6 +297,19 @@ export class ToolManager {
         console.log(`[ToolManager] Unregistered function tool: ${name}`);
     }
 
+    /**
+    * Parse tool call parameters -- they're usually JSON, but they can also be empty strings (which are not valid JSON apparently).
+    * @param {object} parameters The parameters for a tool call, usually a string with JSON inside
+    * @returns {object} The parsed parameters
+    */
+    static #parseParameters(parameters) {
+        return parameters === ''
+            ? {}
+            : typeof parameters === 'string'
+                ? JSON.parse(parameters)
+                : parameters;
+    }
+
     /**
      * Invokes a tool by name. Returns the result of the tool's action function.
      * @param {string} name The name of the tool to invoke.
@@ -309,7 +322,7 @@ export class ToolManager {
                 throw new Error(`No tool with the name "${name}" has been registered.`);
             }
 
-            const invokeParameters = typeof parameters === 'string' ? JSON.parse(parameters) : parameters;
+            const invokeParameters = this.#parseParameters(parameters);
             const tool = this.#tools.get(name);
             const result = await tool.invoke(invokeParameters);
             return typeof result === 'string' ? result : JSON.stringify(result);
@@ -352,7 +365,7 @@ export class ToolManager {
 
         try {
             const tool = this.#tools.get(name);
-            const formatParameters = typeof parameters === 'string' ? JSON.parse(parameters) : parameters;
+            const formatParameters = this.#parseParameters(parameters);
             return await tool.formatMessage(formatParameters);
         } catch (error) {
             console.error(`[ToolManager] An error occurred while formatting the tool call message for "${name}":`, error);