diff --git a/paths/customer_basic.yaml b/paths/customer_basic.yaml
index a633d2b..f823864 100644
--- a/paths/customer_basic.yaml
+++ b/paths/customer_basic.yaml
@@ -24,7 +24,11 @@ get:
                     type: string
                   officialName:
                     type: string
-                  agb:
+                  practiceAgb:
+                    description: The AGB of the practice, if the customer in the response is a practice, otherwise omitted. One of practiceAgb or institutionAgb is always present.
+                    $ref: ../schemas/agb.yaml
+                  institutionAgb:
+                    description: The AGB of the institution, if the customer is a care group or other institute, otherwise omitted. One of practiceAgb or institutionAgb is always present.
                     $ref: ../schemas/agb.yaml
                   gpis:
                     $ref: ../schemas/GPIS.yaml
@@ -69,6 +73,9 @@ get:
                             description: Date of signing the data processing agreement.
                             example: 20160501T1344
                             $ref: ../schemas/date.yaml
+                required:
+                  - name
+                  - officialName
     '400':
       description: If the specified customer is not a practice but some other entity, e.g. a care group.
     '401':
diff --git a/schemas/GPIS.yaml b/schemas/GPIS.yaml
index eabe7b3..667127b 100644
--- a/schemas/GPIS.yaml
+++ b/schemas/GPIS.yaml
@@ -1,4 +1,5 @@
-description: "The source of the medical data used to produce this report: which general practitioner information system was used, and when the data was provided."
+description: |-
+  The source of the medical data used to produce this report: which general practitioner information system was used, and when the data was provided. Omitted if no HIS database was imported (yet).
 type: object
 properties:
   gpisType: