Support additionalProperties in open api schema (#5626)

`z.record(z.string())` as a property in tool parameters currently gets
converted to `undefined`, which is invalid and causes an error from
vertex ai.

This now gets converted to `{ type: 'object', additionalProperties: {
type: 'string' } }`, which works

fixes #5628

---------

Co-authored-by: Lars Grammel <lars.grammel@gmail.com>

Author: tjenkinson

.changeset/cold-schools-sip.md

@@ -0,0 +1,5 @@
+---
+'@ai-sdk/google': patch
+---
+
+Support tool schemas that allow additional properties (e.g `z.record(z.string())`)

packages/google/src/convert-json-schema-to-openapi-schema.test.ts

@@ -23,6 +23,53 @@ it('should remove additionalProperties and $schema', () => {
   expect(convertJSONSchemaToOpenAPISchema(input)).toEqual(expected);
 });
 
+it('supports additionalProperties: true', () => {
+  const input: JSONSchema7 = {
+    $schema: 'http://json-schema.org/draft-07/schema#',
+    type: 'object',
+    properties: {
+      name: { type: 'string' },
+      age: { type: 'number' },
+    },
+    additionalProperties: true,
+  };
+
+  const expected = {
+    type: 'object',
+    properties: {
+      name: { type: 'string' },
+      age: { type: 'number' },
+    },
+    additionalProperties: true,
+  };
+
+  expect(convertJSONSchemaToOpenAPISchema(input)).toEqual(expected);
+});
+
+// z.record(z.string())
+it('supports `additionalProperties` as an object', () => {
+  const input: JSONSchema7 = {
+    $schema: 'http://json-schema.org/draft-07/schema#',
+    type: 'object',
+    properties: {
+      name: { type: 'string' },
+      age: { type: 'number' },
+    },
+    additionalProperties: { type: 'string' },
+  };
+
+  const expected = {
+    type: 'object',
+    properties: {
+      name: { type: 'string' },
+      age: { type: 'number' },
+    },
+    additionalProperties: { type: 'string' },
+  };
+
+  expect(convertJSONSchemaToOpenAPISchema(input)).toEqual(expected);
+});
+
 it('should handle nested objects and arrays', () => {
   const input: JSONSchema7 = {
     type: 'object',

packages/google/src/convert-json-schema-to-openapi-schema.ts

@@ -28,6 +28,7 @@ export function convertJSONSchemaToOpenAPISchema(
     const: constValue,
     minLength,
     enum: enumValues,
+    additionalProperties,
   } = jsonSchema;
 
   const result: Record<string, unknown> = {};
@@ -115,6 +116,13 @@ export function convertJSONSchemaToOpenAPISchema(
     result.minLength = minLength;
   }
 
+  if (additionalProperties === true) {
+    result.additionalProperties = true;
+  } else if (additionalProperties) {
+    result.additionalProperties =
+      convertJSONSchemaToOpenAPISchema(additionalProperties);
+  }
+
   return result;
 }
 
@@ -124,6 +132,7 @@ function isEmptyObjectSchema(jsonSchema: JSONSchema7Definition): boolean {
     typeof jsonSchema === 'object' &&
     jsonSchema.type === 'object' &&
     (jsonSchema.properties == null ||
-      Object.keys(jsonSchema.properties).length === 0)
+      Object.keys(jsonSchema.properties).length === 0) &&
+    !jsonSchema.additionalProperties
   );
 }