diff --git a/.changeset/heavy-badgers-jog.md b/.changeset/heavy-badgers-jog.md
new file mode 100644
index 000000000..e4764a07e
--- /dev/null
+++ b/.changeset/heavy-badgers-jog.md
@@ -0,0 +1,8 @@
+---
+"@logto/core": patch
+---
+
+fix OpenAPI schema returned by the `GET /api/swagger.json` endpoint
+
+1. The `:` character is invalid in parameter names, such as `organizationId:root`. These characters have been replaced with `-`.
+2. The `tenantId` parameter of the `/api/.well-known/endpoints/{tenantId}` route was missing from the generated OpenAPI spec document, resulting in validation errors. This has been fixed.
diff --git a/packages/core/src/routes/swagger/index.test.ts b/packages/core/src/routes/swagger/index.test.ts
index 769a64fe5..7444f2d67 100644
--- a/packages/core/src/routes/swagger/index.test.ts
+++ b/packages/core/src/routes/swagger/index.test.ts
@@ -120,7 +120,7 @@ describe('GET /swagger.json', () => {
         get: {
           parameters: [
             {
-              $ref: '#/components/parameters/mockId:root',
+              $ref: '#/components/parameters/mockId-root',
             },
             {
               name: 'field',
@@ -135,7 +135,7 @@ describe('GET /swagger.json', () => {
         get: {
           parameters: [
             {
-              $ref: '#/components/parameters/mockId:root',
+              $ref: '#/components/parameters/mockId-root',
             },
             {
               name: 'field',
diff --git a/packages/core/src/routes/swagger/index.ts b/packages/core/src/routes/swagger/index.ts
index 94bb7fc4a..b8ab38b45 100644
--- a/packages/core/src/routes/swagger/index.ts
+++ b/packages/core/src/routes/swagger/index.ts
@@ -35,6 +35,7 @@ import {
   paginationParameters,
   buildPathIdParameters,
   mergeParameters,
+  customParameters,
 } from './utils/parameters.js';
 
 type RouteObject = {
@@ -242,8 +243,11 @@ export default function swaggerRoutes<T extends AnonymousRouter, R extends Route
       components: {
         schemas: translationSchemas,
         parameters: identifiableEntityNames.reduce(
-          (previous, entityName) => ({ ...previous, ...buildPathIdParameters(entityName) }),
-          {}
+          (previous, entityName) => ({
+            ...previous,
+            ...buildPathIdParameters(entityName),
+          }),
+          customParameters()
         ),
       },
       tags: [...tags, ...additionalTags].map((tag) => ({ name: tag })),
diff --git a/packages/core/src/routes/swagger/utils/parameters.ts b/packages/core/src/routes/swagger/utils/parameters.ts
index 49bbd20a6..a3bccbc50 100644
--- a/packages/core/src/routes/swagger/utils/parameters.ts
+++ b/packages/core/src/routes/swagger/utils/parameters.ts
@@ -48,7 +48,7 @@ type BuildParameters = {
    * For path parameters, this function will try to match reusable ID parameters:
    *
    * - If the parameter name is `id`, and the path is `/organizations/{id}/users`, the parameter
-   *   `id` will be a reference to `#/components/parameters/organizationId:root`.
+   *   `id` will be a reference to `#/components/parameters/organizationId-root`.
    * - If the parameter name ends with `Id`, and the path is `/organizations/{id}/users/{userId}`,
    *   the parameter `userId` will be a reference to `#/components/parameters/userId`.
    *
@@ -91,7 +91,7 @@ export const buildParameters: BuildParameters = (
       if (key === 'id') {
         if (rootComponent) {
           return {
-            $ref: `#/components/parameters/${pluralize(rootComponent, 1)}Id:root`,
+            $ref: `#/components/parameters/${pluralize(rootComponent, 1)}Id-root`,
           };
         }
 
@@ -206,7 +206,7 @@ export const mergeParameters = (destination: unknown[], source: unknown[]) => {
  *       type: 'string',
  *     },
  *   },
- *   'organizationId:root': {
+ *   'organizationId-root': {
  *     name: 'id',
  *     // ... same as above
  *   },
@@ -216,7 +216,7 @@ export const mergeParameters = (destination: unknown[], source: unknown[]) => {
  * @remarks
  * The root path component is the first path component in the path. For example, the root path
  * component of `/organizations/{id}/users` is `organizations`. Since the name of the parameter is
- * same for all root path components, we need to add an additional key with the `:root` suffix to
+ * same for all root path components, we need to add an additional key with the `-root` suffix to
  * distinguish them.
  *
  * @param rootComponent The root path component in kebab case (`foo-bar`).
@@ -241,7 +241,7 @@ export const buildPathIdParameters = (
   // Need to duplicate the object because OpenAPI does not support partial reference.
   // See https://github.com/OAI/OpenAPI-Specification/issues/2026
   return {
-    [`${entityId}:root`]: {
+    [`${entityId}-root`]: {
       ...shared,
       name: 'id',
     },
@@ -251,3 +251,20 @@ export const buildPathIdParameters = (
     },
   };
 };
+
+/**
+ * Build a parameter object with additional parameters that are not inferred from the path.
+ */
+export const customParameters = (): Record<string, OpenAPIV3.ParameterObject> => {
+  return Object.freeze({
+    tenantId: {
+      name: 'tenantId',
+      in: 'path',
+      description: 'The unique identifier of the tenant.',
+      required: true,
+      schema: {
+        type: 'string',
+      },
+    },
+  });
+};