diff --git a/core/src/tools/openapi_tool/openapi_spec_parser/operation_parser.ts b/core/src/tools/openapi_tool/openapi_spec_parser/operation_parser.ts
index 419a3b23f..0099fccbf 100644
--- a/core/src/tools/openapi_tool/openapi_spec_parser/operation_parser.ts
+++ b/core/src/tools/openapi_tool/openapi_spec_parser/operation_parser.ts
@@ -29,6 +29,13 @@ export class OperationParser {
   private returnValue?: ApiParameter;
   private preservePropertyNames: boolean;
 
+  /**
+   * @param operation The OpenAPI operation to parse.
+   * @param options.preservePropertyNames Keeps the spec's own spelling for
+   *   parameter and request-body property names instead of converting them to
+   *   snake_case. It applies to those names only; the tool name from
+   *   {@link getFunctionName} is always snake_case.
+   */
   constructor(
     private readonly operation: OpenAPIV3.OperationObject,
     options: {preservePropertyNames?: boolean} = {},
@@ -211,6 +218,9 @@ export class OperationParser {
   /**
    * Gets a valid tool function name derived from the operation's operationId.
    *
+   * The name is always snake_case, then truncated to 60 characters.
+   * `preservePropertyNames` does not affect it, matching adk-python.
+   *
    * @throws {Error} If the operation does not have an operationId.
    * @returns A string representing the function name.
    */
@@ -220,7 +230,7 @@ export class OperationParser {
     if (!operationId) {
       throw new Error('Operation ID is missing');
     }
-    return this.getParamName(operationId).substring(0, 60);
+    return snakeCase(operationId).substring(0, 60);
   }
 
   /**
diff --git a/core/test/tools/openapi_tool/openapi_toolset_test.ts b/core/test/tools/openapi_tool/openapi_toolset_test.ts
index da2e32380..a4c43c5b5 100644
--- a/core/test/tools/openapi_tool/openapi_toolset_test.ts
+++ b/core/test/tools/openapi_tool/openapi_toolset_test.ts
@@ -174,6 +174,47 @@ describe('OpenAPIToolset', () => {
     const toolset = new OpenAPIToolset({specDict: mockSpec});
     await expect(toolset.close()).resolves.toBeUndefined();
   });
+
+  it('should snake_case the tool name while preserving property names', async () => {
+    const camelCaseSpec: OpenAPIV3.Document = {
+      openapi: '3.0.0',
+      info: {title: 'Test API', version: '1.0.0'},
+      servers: [{url: 'https://api.example.com'}],
+      paths: {
+        '/users': {
+          post: {
+            operationId: 'createUser',
+            requestBody: {
+              content: {
+                'application/json': {
+                  schema: {
+                    type: 'object',
+                    properties: {
+                      firstName: {type: 'string'},
+                      lastName: {type: 'string'},
+                      emailAddress: {type: 'string'},
+                    },
+                  },
+                },
+              },
+            },
+            responses: {'200': {description: 'OK'}},
+          },
+        },
+      },
+    };
+
+    const toolset = new OpenAPIToolset({
+      specDict: camelCaseSpec,
+      preservePropertyNames: true,
+    });
+    const tools = await toolset.getTools();
+
+    expect(tools.map((tool) => tool.name)).toEqual(['create_user']);
+    expect(
+      Object.keys(tools[0]._getDeclaration()?.parameters?.properties ?? {}),
+    ).toEqual(['firstName', 'lastName', 'emailAddress']);
+  });
 });
 
 describe('OpenApiSpecParser', () => {
diff --git a/core/test/tools/openapi_tool/operation_parser_test.ts b/core/test/tools/openapi_tool/operation_parser_test.ts
index 4d76ffc64..a52794344 100644
--- a/core/test/tools/openapi_tool/operation_parser_test.ts
+++ b/core/test/tools/openapi_tool/operation_parser_test.ts
@@ -204,4 +204,84 @@ describe('OperationParser', () => {
 
     expect(new OperationParser(op).getParameters()[0].name).toBe('');
   });
+
+  it.each([false, true])(
+    'should snake_case the tool name with preservePropertyNames %s',
+    (preservePropertyNames) => {
+      const op: OpenAPIV3.OperationObject = {
+        operationId: 'listIssues',
+        responses: {},
+      };
+
+      expect(
+        new OperationParser(op, {preservePropertyNames}).getFunctionName(),
+      ).toBe('list_issues');
+    },
+  );
+
+  it('should convert the tool name while preserving body property names', () => {
+    const op: OpenAPIV3.OperationObject = {
+      operationId: 'createUser',
+      requestBody: {
+        content: {
+          'application/json': {
+            schema: {
+              type: 'object',
+              properties: {
+                firstName: {type: 'string'},
+                lastName: {type: 'string'},
+                emailAddress: {type: 'string'},
+              },
+            },
+          },
+        },
+      },
+      responses: {'200': {description: 'OK'}},
+    };
+
+    const parser = new OperationParser(op, {preservePropertyNames: true});
+
+    expect(parser.getFunctionName()).toBe('create_user');
+    expect(parser.getParameters().map((p) => p.name)).toEqual([
+      'firstName',
+      'lastName',
+      'emailAddress',
+    ]);
+  });
+
+  it('should convert the tool name while preserving operation parameter names', () => {
+    const op: OpenAPIV3.OperationObject = {
+      operationId: 'jira_list_Issues',
+      parameters: [
+        {name: 'X-API-Key', in: 'header'},
+        {name: 'Issue_Id', in: 'query'},
+      ],
+      responses: {},
+    };
+
+    const parser = new OperationParser(op, {preservePropertyNames: true});
+
+    expect(parser.getFunctionName()).toBe('jira_list_issues');
+    expect(parser.getParameters().map((p) => p.name)).toEqual([
+      'X-API-Key',
+      'Issue_Id',
+    ]);
+  });
+
+  it('should truncate the preserved-name tool name after conversion', () => {
+    const op: OpenAPIV3.OperationObject = {
+      operationId:
+        'listIssuesForTheRepositoryWithAVeryLongOperationIdentifierName',
+      responses: {},
+    };
+
+    const name = new OperationParser(op, {
+      preservePropertyNames: true,
+    }).getFunctionName();
+
+    expect(name).toBe(
+      'list_issues_for_the_repository_with_a_very_long_operation_id',
+    );
+    expect(name.length).toBe(60);
+  });
 });