diff --git a/packages/behavior/context/context.hooks.js b/packages/behavior/context/context.hooks.js
index 499a3e7..499d976 100644
--- a/packages/behavior/context/context.hooks.js
+++ b/packages/behavior/context/context.hooks.js
@@ -2,24 +2,32 @@ import {Context} from './context';
 
 export function behaviorContextTypes() {
   return {
-    bool: {},
+    bool: {
+      defaultLiteral: true,
+    },
     context: {
-      add: {
-        type: 'void',
-        label: 'Add $2 as $1.',
-        args: [
-          ['key', {
-            type: 'string',
-          }],
-          ['value', {
-            type: 'any',
-          }],
-        ],
+      children: {
+        add: {
+          type: 'void',
+          label: 'Add $2 as $1.',
+          args: [
+            ['key', {
+              type: 'string',
+            }],
+            ['value', {
+              type: 'any',
+            }],
+          ],
+        },
       },
     },
-    number: {},
+    number: {
+      defaultLiteral: 0,
+    },
     stream: {},
-    string: {},
+    string: {
+      defaultLiteral: '',
+    },
     void: {},
   };
 }
diff --git a/packages/behavior/context/context.js b/packages/behavior/context/context.js
index 6dd24b2..e6533b1 100644
--- a/packages/behavior/context/context.js
+++ b/packages/behavior/context/context.js
@@ -60,7 +60,7 @@ export class Context {
     }
     const description = this.typeDescription(type, undefined);
     const subtypes = Object.keys(
-      Object.values(description)
+      Object.values(description.children)
         .reduce((r, spec) => ({...r, [spec.type]: true}), {})
     );
     subtypes.forEach((type) => marked[type] = true);
@@ -78,15 +78,18 @@ export class Context {
     if (!types[type]) {
       return {};
     }
-    if ('function' === typeof types[type]) {
-      return types[type](variable);
-    }
-    return types[type];
+    return {
+      children: {},
+      ...('function' === typeof types[type] ? types[type](variable) : types[type])
+    };
   }
 
   static types() {
     return invokeHookFlat('behaviorContextTypes')
-      .reduce((r, results) => ({...r, ...results}), {});
+      .reduce((r, results) => ({
+        ...r,
+        ...results,
+      }), {});
   }
 
   add(key, value, type) {
diff --git a/packages/behavior/context/flow.hooks.js b/packages/behavior/context/flow.hooks.js
index 4abf8a3..0a407b9 100644
--- a/packages/behavior/context/flow.hooks.js
+++ b/packages/behavior/context/flow.hooks.js
@@ -27,35 +27,37 @@ export function behaviorContextGlobals() {
 export function behaviorContextTypes() {
   return {
     Flow: {
-      conditional: {
-        type: 'bool',
-        label: 'If $1 then run $2.',
-        args: [
-          ['condition', {
-            type: 'condition',
-          }],
-          ['actions', {
-            type: 'actions',
-          }],
-        ],
-      },
-      parallel: {
-        type: 'void',
-        label: 'Run $1 in parallel.',
-        args: [
-          ['actions', {
-            type: 'actions',
-          }],
-        ],
-      },
-      serial: {
-        type: 'void',
-        label: 'Run $1 serially.',
-        args: [
-          ['actions', {
-            type: 'actions',
-          }],
-        ],
+      children: {
+        conditional: {
+          type: 'bool',
+          label: 'If $1 then run $2.',
+          args: [
+            ['condition', {
+              type: 'condition',
+            }],
+            ['actions', {
+              type: 'actions',
+            }],
+          ],
+        },
+        parallel: {
+          type: 'void',
+          label: 'Run $1 in parallel.',
+          args: [
+            ['actions', {
+              type: 'actions',
+            }],
+          ],
+        },
+        serial: {
+          type: 'void',
+          label: 'Run $1 serially.',
+          args: [
+            ['actions', {
+              type: 'actions',
+            }],
+          ],
+        },
       },
     },
   };
diff --git a/packages/behavior/context/timing.hooks.js b/packages/behavior/context/timing.hooks.js
index fb4695f..41db66b 100644
--- a/packages/behavior/context/timing.hooks.js
+++ b/packages/behavior/context/timing.hooks.js
@@ -19,14 +19,16 @@ class Timing {
 export function behaviorContextTypes() {
   return {
     Timing: {
-      wait: {
-        type: 'void',
-        label: 'Wait for $1 seconds.',
-        args: [
-          ['duration', {
-            type: 'number',
-          }],
-        ],
+      children: {
+        wait: {
+          type: 'void',
+          label: 'Wait for $1 seconds.',
+          args: [
+            ['duration', {
+              type: 'number',
+            }],
+          ],
+        },
       },
     },
   };
diff --git a/packages/behavior/context/utility.hooks.js b/packages/behavior/context/utility.hooks.js
index 9f3a581..637687c 100644
--- a/packages/behavior/context/utility.hooks.js
+++ b/packages/behavior/context/utility.hooks.js
@@ -35,25 +35,27 @@ class Utility {
 export function behaviorContextTypes() {
   return {
     Utility: {
-      makeArray: {
-        type: 'array',
-        label: 'Make array.',
-        args: [],
-      },
-      makeObject: {
-        type: 'object',
-        label: 'Make object.',
-        args: [],
-      },
-      log: {
-        type: 'void',
-        label: 'Log.',
-        args: [],
-      },
-      merge: {
-        type: 'object',
-        label: 'Merge objects.',
-        args: [],
+      children: {
+        makeArray: {
+          type: 'array',
+          label: 'Make array.',
+          args: [],
+        },
+        makeObject: {
+          type: 'object',
+          label: 'Make object.',
+          args: [],
+        },
+        log: {
+          type: 'void',
+          label: 'Log.',
+          args: [],
+        },
+        merge: {
+          type: 'object',
+          label: 'Merge objects.',
+          args: [],
+        },
       },
     },
   };
diff --git a/packages/entity/index.hooks.js b/packages/entity/index.hooks.js
index 4b672d1..9be6490 100644
--- a/packages/entity/index.hooks.js
+++ b/packages/entity/index.hooks.js
@@ -5,24 +5,23 @@ export function behaviorContextTypes() {
       const Traits = entity
         ? Object.values(entity.allTraitInstances()).map((instance) => instance.constructor)
         : allTraits();
-      const traitTypes = Traits
-        .reduce((r, {behaviorContextTypes, describeState}) => ({
-          ...r,
-          ...behaviorContextTypes(),
-          ...describeState(),
-        }), {});
-      return {
-        ...traitTypes,
-        invokeHook: {
-          type: 'object',
-          label: 'Invoke hook.',
-          args: [
-            ['hook', {
-              type: 'string',
-            }],
-          ],
-        },
+      const core = {
+        children: {
+          invokeHook: {
+            type: 'object',
+            label: 'Invoke hook.',
+            args: [
+              ['hook', {
+                type: 'string',
+              }],
+            ],
+          },
+        }
       };
+      return Traits
+        .reduce((r, T) => ({
+          ...r, children: {...r.children, ...T.behaviorContextTypes(), ...T.describeState()},
+        }), core);
     },
   };
 }
diff --git a/packages/math/index.hooks.js b/packages/math/index.hooks.js
index 6b90766..594dd99 100644
--- a/packages/math/index.hooks.js
+++ b/packages/math/index.hooks.js
@@ -9,30 +9,32 @@ export function behaviorContextGlobals() {
 export function behaviorContextTypes() {
   return {
     Math: (Math) => ({
-      floor: {
-        type: 'number',
-        label: 'Floor $1.',
-        args: [
-          ['operand', {
-            type: 'number',
-          }],
-        ],
-      },
-      randomNumber: {
-        type: 'number',
-        label: 'Random number between $1 and $2.',
-        args: [
-          ['min', {
-            type: 'number',
-          }],
-          ['max', {
-            type: 'number',
-          }],
-        ],
-      },
-      Vector: {
-        type: 'Vector',
-      },
+      children: {
+        floor: {
+          type: 'number',
+          label: 'Floor $1.',
+          args: [
+            ['operand', {
+              type: 'number',
+            }],
+          ],
+        },
+        randomNumber: {
+          type: 'number',
+          label: 'Random number between $1 and $2.',
+          args: [
+            ['min', {
+              type: 'number',
+            }],
+            ['max', {
+              type: 'number',
+            }],
+          ],
+        },
+        Vector: {
+          type: 'Vector',
+        },
+      }
     }),
   };
 }
diff --git a/packages/math/vector/index.hooks.js b/packages/math/vector/index.hooks.js
index 60b29d7..1b7155e 100644
--- a/packages/math/vector/index.hooks.js
+++ b/packages/math/vector/index.hooks.js
@@ -1,35 +1,50 @@
 export function behaviorContextTypes() {
   return {
+    vector: {
+      defaultLiteral: [0, 0],
+      children: {
+        x: {
+          type: 'number',
+          label: 'X',
+        },
+        y: {
+          type: 'number',
+          label: 'Y',
+        },
+      },
+    },
     Vector: (Math) => ({
-      floor: {
-        type: 'vector',
-        label: 'Floor $1.',
-        args: [
-          ['vector', {
-            type: 'vector',
-          }],
-        ],
-      },
-      fromDirection: {
-        type: 'vector',
-        label: '$1 as a movement vector.',
-        args: [
-          ['direction', {
-            type: 'number',
-          }],
-        ],
-      },
-      sub: {
-        type: 'vector',
-        label: 'Subtract $2 from $1.',
-        args: [
-          ['l', {
-            type: 'vector',
-          }],
-          ['r', {
-            type: 'vector',
-          }],
-        ],
+      children: {
+        floor: {
+          type: 'vector',
+          label: 'Floor $1.',
+          args: [
+            ['vector', {
+              type: 'vector',
+            }],
+          ],
+        },
+        fromDirection: {
+          type: 'vector',
+          label: '$1 as a movement vector.',
+          args: [
+            ['direction', {
+              type: 'number',
+            }],
+          ],
+        },
+        sub: {
+          type: 'vector',
+          label: 'Subtract $2 from $1.',
+          args: [
+            ['l', {
+              type: 'vector',
+            }],
+            ['r', {
+              type: 'vector',
+            }],
+          ],
+        },
       },
     }),
   };