diff --git a/docs/API.md b/docs/API.md
index 2cdce6f0..fcb769f5 100644
--- a/docs/API.md
+++ b/docs/API.md
@@ -69,6 +69,8 @@ Maintainerr exposes lightweight health endpoints under `/api/health` (prefixed w
 | `POST /api/collections/:id/poster`   | Upload a custom collection poster with multipart field `poster`; returns `{ pushed, attempted }`  |
 | `DELETE /api/collections/:id/poster` | Clear the stored poster and return `{ cleared, refreshRequested }`                                |
 
+The lower-level `POST /api/media-server/collection` request body matches `CreateCollectionParams`: `libraryId`, `title`, and `type` are required, with optional `summary`, `sortTitle`, and `initialItemId`. `initialItemId` is a single media-server item id used when a collection must be created with one initial member; remaining items are still added afterwards through the normal collection-sync path.
+
 ### Metadata
 
 | Endpoint                                        | Purpose                                                                             |
diff --git a/static/openapi-spec/maintainerr_api_specs.yaml b/static/openapi-spec/maintainerr_api_specs.yaml
index f6deb1f7..b462b524 100644
--- a/static/openapi-spec/maintainerr_api_specs.yaml
+++ b/static/openapi-spec/maintainerr_api_specs.yaml
@@ -743,6 +743,12 @@ paths:
     post:
       operationId: MediaServerController_createCollection
       parameters: []
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/CreateCollectionParams'
       responses:
         '201':
           description: ''
@@ -2122,6 +2128,31 @@ components:
           type: boolean
         recommended:
           type: boolean
+    CreateCollectionParams:
+      type: object
+      properties:
+        libraryId:
+          type: string
+        title:
+          type: string
+        summary:
+          type: string
+        type:
+          type: string
+          enum:
+            - movie
+            - show
+            - season
+            - episode
+        sortTitle:
+          type: string
+        initialItemId:
+          type: string
+          description: Optional id of a single media-server item to include when the collection is created.
+      required:
+        - libraryId
+        - title
+        - type
     RulesDto:
       type: object
       properties: {}