diff --git a/design/design.yml b/design/design.yml
new file mode 100644
index 00000000..2047e243
--- /dev/null
+++ b/design/design.yml
@@ -0,0 +1,79 @@
+rules:
+  openapi-v3-limit-number-of-sub-resources:
+    description: Ensures that there are not too many sub-resources.
+    message: There should be no more than three levels of sub-resources.
+    severity: warn
+    given: $.paths.*~
+    then:
+      function: pattern
+      functionOptions:
+        match: ^/[^/]*((/{[^}]*})*/[^/]*(/{[^}]*})*){0,3}/?$
+  openapi-v3-limit-number-of-paths:
+    description: Ensures that there are not too many paths.
+    message: There should be no more than 10 paths.
+    severity: warn
+    given: $.paths
+    then:
+      function: count-resource-types
+      functionOptions:
+        max: 10
+  openapi-v3-parameters-name-length:
+    description: Ensures that that parameter names aren't too long.
+    message: Your parameter names should not be longer than 25 characters.
+    given:
+    - $.paths.*.parameters[?(@.in=='query')]
+    - $.components.parameters.[?(@.in=='query')]
+    then:
+      field: name
+      function: length
+      functionOptions:
+        max: 25
+
+  # Max length.
+  openapi-v3-description-max-length:
+    description: |-
+      Ensures that all APIs descriptions and summaries are under a specific length.
+    given:
+    - $.info
+    - $.paths.*
+    severity: hint
+    recommended: true
+    type: style
+    formats:
+      - oas3
+    then:
+    - field: description
+      function: length
+      functionOptions:
+        max: 500
+    - field: description
+      function: length
+      functionOptions:
+        max: 120
+
+  openapi-v3-info-summary-word-check:
+    description: Ensures that all OpenAPIs information object summary do not contain
+      some words.
+    message: The info object summary should not contain the words REST, Public, or
+      Developer.
+    given: $.info.summary
+    severity: error
+    recommended: true
+    type: style
+    formats:
+      - oas3
+    then:
+      function: pattern
+      functionOptions:
+        notMatch: \b(REST|Public|Developer)\b
+  # Examples
+  openapi-v3-parameters-example:
+    description: Ensures that that all parameters have a examples.
+    message: Your parameters all need examples.
+    given:
+    - $.paths.*.*.parameters[?(@.example=='query')]
+    then:
+      - field: example
+        function: truthy
+      - field: examples
+        function: truthy
diff --git a/design/tests/design-test.snapshot b/design/tests/design-test.snapshot
new file mode 100644
index 00000000..578b3a19
--- /dev/null
+++ b/design/tests/design-test.snapshot
@@ -0,0 +1,9 @@
+OpenAPI 3.x detected
+
+/code/design/tests/design-test.yml
+ 14:14  warning  openapi-v3-limit-number-of-sub-resources  There should be no more than three levels of sub-resources.    paths./a/b/c/d/e
+ 16:15  warning  openapi-v3-parameters-name-length         Your parameter names should not be longer than 25 characters.  paths./a/b/c/d/e.parameters[0].name
+ 35:13  warning  openapi-v3-parameters-name-length         Your parameter names should not be longer than 25 characters.  components.parameters.MyParam.name
+
+✖ 3 problems (0 errors, 3 warnings, 0 infos, 0 hints)
+
diff --git a/design/tests/design-test.yml b/design/tests/design-test.yml
new file mode 100644
index 00000000..0870583a
--- /dev/null
+++ b/design/tests/design-test.yml
@@ -0,0 +1,38 @@
+openapi: 3.0.1
+servers: []
+paths:
+  /a1: {}
+  /a2: {}
+  /a3: {}
+  /a4: {}
+  /a5: {}
+  /a6: {}
+  /a7: {}
+  /a8: {}
+  /a9: {}
+  /a10: {}
+  /a/b/c/d/e:
+    parameters:
+      - name: fooo_baar_antani_sblindola_monoteca
+        in: query
+        schema:
+          type: string
+
+tags: []
+info:
+  version: 1.2.3
+  contact:
+    name: ciao
+    email: a@b.it
+  title: foo
+  description: ciao
+  x-summary: >-
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+
+components:
+  parameters:
+    MyParam:
+      name: fooo_baar_antani_sblindola_monoteca
+      in: query
+      schema:
+        type: string