diff --git a/public/openapi/read.yaml b/public/openapi/read.yaml
index 9c710781d0..14ed40e1d4 100644
--- a/public/openapi/read.yaml
+++ b/public/openapi/read.yaml
@@ -356,7 +356,9 @@ paths:
     $ref: 'read/groups/slug.yaml'
   "/api/groups/{slug}/members":
     $ref: 'read/groups/slug/members.yaml'
-  "/api/world":
+  /api/world:
     $ref: 'read/world.yaml'
+  /api/ap:
+    $ref: 'read/ap.yaml'
   /api/outgoing:
     $ref: 'read/outgoing.yaml'
\ No newline at end of file
diff --git a/public/openapi/read/admin/config.yaml b/public/openapi/read/admin/config.yaml
index f79df9eca6..dcfbcaffc1 100644
--- a/public/openapi/read/admin/config.yaml
+++ b/public/openapi/read/admin/config.yaml
@@ -142,6 +142,11 @@ get:
                 properties:
                   size:
                     type: number
+              activitypub:
+                type: object
+                properties:
+                  probe:
+                    type: number
               acpLang:
                 type: string
               openOutgoingLinksInNewTab:
diff --git a/public/openapi/read/ap.yaml b/public/openapi/read/ap.yaml
new file mode 100644
index 0000000000..0704cc6dab
--- /dev/null
+++ b/public/openapi/read/ap.yaml
@@ -0,0 +1,31 @@
+get:
+  tags:
+    - activitypub
+  summary: Fetch URL for in-app processing
+  description: |
+    This route accepts a URL in the `resource` query parameter, and runs some quick tests to
+    determine whether that address points to an ActivityPub resource. If so, then it will try
+    to process it locally and redirect the user to the local representation of it.
+
+    If there is no local representation available, then the user is sent off-site as originally
+    expected.
+  parameters:
+    - in: query
+      name: resource
+      schema:
+        type: string
+      description: A URL to query for potential ActivityPub resource
+      example: 'https://example.org/ap'
+  responses:
+    "200":
+      description: Sent if the `/api` prefix is used. The `X-Redirect` header is sent with the redirection target.
+      headers:
+        'X-Redirect':
+          schema:
+            type: string
+    "307":
+      description: Redirect the user to the local representation or original URL.
+      headers:
+        Location:
+          schema:
+            type: string
\ No newline at end of file
diff --git a/public/openapi/read/config.yaml b/public/openapi/read/config.yaml
index 3b38168c2e..77c31d871b 100644
--- a/public/openapi/read/config.yaml
+++ b/public/openapi/read/config.yaml
@@ -174,3 +174,8 @@ get:
                       type: string
                   version:
                     type: string
+              activitypub:
+                type: object
+                properties:
+                  probe:
+                    type: number
\ No newline at end of file