diff --git a/.vscode/settings.json b/.vscode/settings.json
index 6de9fd00..93b727f4 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -20,6 +20,7 @@
     "nearley",
     "ngraph",
     "ostrio",
+    "recomputation",
     "Ruleset",
     "snackbars",
     "Spellcasting",
diff --git a/app/imports/api/creature/creatureProperties/CreatureProperties.ts b/app/imports/api/creature/creatureProperties/CreatureProperties.ts
index c346e8c6..ac4a062d 100644
--- a/app/imports/api/creature/creatureProperties/CreatureProperties.ts
+++ b/app/imports/api/creature/creatureProperties/CreatureProperties.ts
@@ -6,31 +6,9 @@ import SoftRemovableSchema from '/imports/api/parenting/SoftRemovableSchema';
 import propertySchemasIndex from '/imports/api/properties/computedPropertySchemasIndex';
 import { storedIconsSchema } from '/imports/api/icons/Icons';
 import STORAGE_LIMITS from '/imports/constants/STORAGE_LIMITS';
+import { InferType, TypedSimpleSchema } from '/imports/api/utility/TypedSimpleSchema';
 
-// TODO make this a union type of all CreatureProperty types
-const CreatureProperties: Mongo.Collection<any> = new Mongo.Collection('creatureProperties');
-
-export interface CreatureProperty extends TreeDoc {
-  _id: string
-  _migrationError?: string
-  tags: string[]
-  type: string
-  disabled?: boolean
-  icon?: {
-    name: string
-    shape: string
-  },
-  libraryNodeId?: string
-  slotQuantityFilled?: number
-  inactive?: boolean
-  deactivatedByAncestor?: boolean
-  deactivatedBySelf?: boolean
-  deactivatedByToggle?: boolean
-  deactivatingToggleId?: boolean
-  dirty?: boolean
-}
-
-const CreaturePropertySchema = new SimpleSchema({
+const PreComputeCreaturePropertySchema = new TypedSimpleSchema({
   _id: {
     type: String,
     regEx: SimpleSchema.RegEx.Id,
@@ -75,13 +53,12 @@ const CreaturePropertySchema = new SimpleSchema({
   },
 });
 
-const DenormalisedOnlyCreaturePropertySchema = new SimpleSchema({
+const DenormalisedOnlyCreaturePropertySchema = new TypedSimpleSchema({
   // Denormalised flag if this property is inactive on the sheet for any reason
   // Including being disabled, or a descendant of a disabled property
   inactive: {
     type: Boolean,
     optional: true,
-    index: 1,
     removeBeforeCompute: true,
   },
   // Denormalised flag if this property was made inactive by an inactive
@@ -90,7 +67,6 @@ const DenormalisedOnlyCreaturePropertySchema = new SimpleSchema({
   deactivatedByAncestor: {
     type: Boolean,
     optional: true,
-    index: 1,
     removeBeforeCompute: true,
   },
   // Denormalised flag if this property was made inactive because of its own
@@ -98,7 +74,6 @@ const DenormalisedOnlyCreaturePropertySchema = new SimpleSchema({
   deactivatedBySelf: {
     type: Boolean,
     optional: true,
-    index: 1,
     removeBeforeCompute: true,
   },
   // Denormalised flag if this property was made inactive because of a toggle
@@ -106,7 +81,6 @@ const DenormalisedOnlyCreaturePropertySchema = new SimpleSchema({
   deactivatedByToggle: {
     type: Boolean,
     optional: true,
-    index: 1,
     removeBeforeCompute: true,
   },
   deactivatingToggleId: {
@@ -154,9 +128,23 @@ const DenormalisedOnlyCreaturePropertySchema = new SimpleSchema({
   },
 });
 
-CreaturePropertySchema.extend(DenormalisedOnlyCreaturePropertySchema);
+const CreaturePropertySchema = PreComputeCreaturePropertySchema.extend(DenormalisedOnlyCreaturePropertySchema);
 
-for (const key in propertySchemasIndex) {
+type CreaturePropertyByType<T extends keyof typeof propertySchemasIndex> =
+  InferType<typeof propertySchemasIndex[T]>
+  & InferType<typeof CreaturePropertySchema>
+  & InferType<typeof ColorSchema>
+  & InferType<typeof ChildSchema>
+  & InferType<typeof SoftRemovableSchema>
+
+type ConvertToUnion<T> = T[keyof T];
+type CreatureProperty = ConvertToUnion<{ [key in keyof typeof propertySchemasIndex]: CreaturePropertyByType<key> }>;
+type ActionProperty = CreaturePropertyByType<'action'>;
+
+const CreatureProperties = new Mongo.Collection<CreatureProperty>('creatureProperties');
+
+let key: keyof typeof propertySchemasIndex;
+for (key in propertySchemasIndex) {
   const schema = new SimpleSchema({});
   schema.extend(propertySchemasIndex[key]);
   schema.extend(CreaturePropertySchema);
@@ -167,12 +155,13 @@ for (const key in propertySchemasIndex) {
   if (key === 'any') {
     // @ts-expect-error don't have types for .attachSchema
     CreatureProperties.attachSchema(schema);
+  } else {
+    // TODO remove all {selector: {type: any}} options
+    // @ts-expect-error don't have types for .attachSchema
+    CreatureProperties.attachSchema(schema, {
+      selector: { type: key }
+    });
   }
-  // TODO make this an else branch and remove all {selector: {type: any}} options
-  // @ts-expect-error don't have types for .attachSchema
-  CreatureProperties.attachSchema(schema, {
-    selector: { type: key }
-  });
 }
 
 export default CreatureProperties;
diff --git a/app/imports/api/icons/Icons.js b/app/imports/api/icons/Icons.ts
similarity index 80%
rename from app/imports/api/icons/Icons.js
rename to app/imports/api/icons/Icons.ts
index eb2f8fe1..5a85af7a 100644
--- a/app/imports/api/icons/Icons.js
+++ b/app/imports/api/icons/Icons.ts
@@ -3,10 +3,9 @@ import { ValidatedMethod } from 'meteor/mdg:validated-method';
 import { RateLimiterMixin } from 'ddp-rate-limiter-mixin';
 import { assertAdmin } from '/imports/api/sharing/sharingPermissions';
 import STORAGE_LIMITS from '/imports/constants/STORAGE_LIMITS';
+import { InferType, TypedSimpleSchema } from '/imports/api/utility/TypedSimpleSchema';
 
-let Icons = new Mongo.Collection('icons');
-
-let iconsSchema = new SimpleSchema({
+const iconsSchema = new TypedSimpleSchema({
   name: {
     type: String,
     unique: true,
@@ -34,6 +33,12 @@ let iconsSchema = new SimpleSchema({
   },
 });
 
+type Icon = InferType<typeof iconsSchema>;
+
+const Icons = new Mongo.Collection<Icon>('icons');
+// @ts-expect-error don't have types for .attachSchema
+Icons.attachSchema(iconsSchema);
+
 if (Meteor.isServer) {
   Icons._ensureIndex({
     'name': 'text',
@@ -42,7 +47,7 @@ if (Meteor.isServer) {
   });
 }
 
-const storedIconsSchema = new SimpleSchema({
+const storedIconsSchema = new TypedSimpleSchema({
   name: {
     type: String,
   },
@@ -51,12 +56,15 @@ const storedIconsSchema = new SimpleSchema({
   },
 });
 
-Icons.attachSchema(iconsSchema);
-
 // This method does not validate icons against the schema, use wisely;
 const writeIcons = new ValidatedMethod({
   name: 'icons.write',
   validate: null,
+  mixins: [RateLimiterMixin],
+  rateLimit: {
+    numRequests: 20,
+    timeInterval: 10000,
+  },
   run(icons) {
     assertAdmin(this.userId);
     if (Meteor.isServer) {
@@ -88,6 +96,7 @@ const findIcons = new ValidatedMethod({
       {
         // relevant documents have a higher score.
         fields: {
+          // @ts-expect-error don't have types for meta text scoring
           score: { $meta: 'textScore' }
         },
         // `score` property specified in the projection fields above.
diff --git a/app/imports/api/properties/Actions.ts b/app/imports/api/properties/Actions.ts
index f4d87bdc..39d4c325 100644
--- a/app/imports/api/properties/Actions.ts
+++ b/app/imports/api/properties/Actions.ts
@@ -7,6 +7,7 @@ import { CreatureProperty } from '/imports/api/creature/creatureProperties/Creat
 import { InlineCalculation } from '/imports/api/properties/subSchemas/inlineCalculationField';
 import { CalculatedField } from '/imports/api/properties/subSchemas/computedField';
 import Property from '/imports/api/properties/Properties.type';
+import { TypedSimpleSchema } from '/imports/api/utility/TypedSimpleSchema';
 
 export type CreatureAction = Action & CreatureProperty & {
   overridden?: boolean
@@ -314,7 +315,7 @@ const ComputedOnlyActionSchema = createPropertySchema({
   },
 });
 
-const ComputedActionSchema = new SimpleSchema()
+const ComputedActionSchema = new TypedSimpleSchema({})
   .extend(ActionSchema)
   .extend(ComputedOnlyActionSchema);
 
diff --git a/app/imports/api/properties/subSchemas/AdjustmentSchema.js b/app/imports/api/properties/subSchemas/AdjustmentSchema.ts
similarity index 76%
rename from app/imports/api/properties/subSchemas/AdjustmentSchema.js
rename to app/imports/api/properties/subSchemas/AdjustmentSchema.ts
index 5ca96137..4f43b034 100644
--- a/app/imports/api/properties/subSchemas/AdjustmentSchema.js
+++ b/app/imports/api/properties/subSchemas/AdjustmentSchema.ts
@@ -1,10 +1,10 @@
-import SimpleSchema from 'simpl-schema';
 import { Random } from 'meteor/random';
+import { InferType, TypedSimpleSchema } from '/imports/api/utility/TypedSimpleSchema';
 
-const AdjustmentSchema = new SimpleSchema({
+const AdjustmentSchema = new TypedSimpleSchema({
   _id: {
     type: String,
-    regEx: SimpleSchema.RegEx.Id,
+    max: 17,
     autoValue() {
       if (!this.isSet) return Random.id();
     }
@@ -23,7 +23,7 @@ const AdjustmentSchema = new SimpleSchema({
       'self',   // the character who took the action
       'each',   // rolled once for `each` target
       'every',  // rolled once and applied to `every` target
-    ],
+    ] as const,
   },
   // The stat this rolls applies to, if damage type is set, this is ignored
   stat: {
@@ -32,4 +32,6 @@ const AdjustmentSchema = new SimpleSchema({
   },
 });
 
+export type Adjustment = InferType<typeof AdjustmentSchema>;
+
 export default AdjustmentSchema;
diff --git a/app/imports/api/properties/subSchemas/ColorSchema.ts b/app/imports/api/properties/subSchemas/ColorSchema.ts
index 34fd807f..70753fa8 100644
--- a/app/imports/api/properties/subSchemas/ColorSchema.ts
+++ b/app/imports/api/properties/subSchemas/ColorSchema.ts
@@ -1,10 +1,6 @@
-import SimpleSchema from 'simpl-schema';
+import { TypedSimpleSchema } from '/imports/api/utility/TypedSimpleSchema';
 
-export interface Colored {
-  color?: string,
-}
-
-const ColorSchema = new SimpleSchema({
+const ColorSchema = new TypedSimpleSchema({
   color: {
     type: String,
     // match hex colors of the form #A23 or #A23f56
diff --git a/app/imports/api/properties/subSchemas/createPropertySchema.js b/app/imports/api/properties/subSchemas/createPropertySchema.ts
similarity index 84%
rename from app/imports/api/properties/subSchemas/createPropertySchema.js
rename to app/imports/api/properties/subSchemas/createPropertySchema.ts
index 2d2d6b11..34a6cde7 100644
--- a/app/imports/api/properties/subSchemas/createPropertySchema.js
+++ b/app/imports/api/properties/subSchemas/createPropertySchema.ts
@@ -6,12 +6,12 @@ import {
   fieldToCompute,
   computedOnlyField,
 } from '/imports/api/properties/subSchemas/computedField';
-import SimpleSchema from 'simpl-schema';
+import { Definition, TypedSimpleSchema } from '/imports/api/utility/TypedSimpleSchema';
 
 // Search through the schema for keys whose type is 'fieldToCompute' etc.
 // replace the type with Object and attach extend the schema with
 // the required fields to make the computation work
-export default function createPropertySchema(definition) {
+export default function createPropertySchema(definition: Definition) {
   const computationFields = {
     inlineCalculationFieldToCompute: [],
     computedOnlyInlineCalculationField: [],
@@ -20,9 +20,9 @@ export default function createPropertySchema(definition) {
   };
   const computedKeys = Object.keys(computationFields);
 
-  for (let key in definition) {
+  for (const key in definition) {
     const def = definition[key];
-    if (computedKeys.includes(def.type)) {
+    if (typeof def === 'object' && 'type' in def && computedKeys.includes(def.type)) {
       computationFields[def.type].push(key);
       applyDefaultCalculationValue(definition, key);
       def.type = Object;
@@ -31,6 +31,7 @@ export default function createPropertySchema(definition) {
           `computed field: '${key}' of '${def.type}' is expected to be optional`
         );
       }
+      //@ts-expect-error removeBeforeCompute is an extension of SimpleSchema
       if (def.removeBeforeCompute) {
         console.warn(
           `computed field: '${key}' of '${def.type}' should not be removed before computation`
@@ -40,7 +41,7 @@ export default function createPropertySchema(definition) {
   }
 
   // Create a schema with the edited definition
-  const schema = new SimpleSchema(definition);
+  const schema = new TypedSimpleSchema(definition);
 
   // Extend the schema with all the computation fields
   computationFields.inlineCalculationFieldToCompute.forEach(key => {
@@ -69,7 +70,7 @@ function applyDefaultCalculationValue(definition, key) {
     // on the fields to compute
     return;
   }
-  let defaultValue = def.defaultValue;
+  const defaultValue = def.defaultValue;
   if (!defaultValue) return;
   let calcField;
   if (def.type === 'fieldToCompute') {
diff --git a/app/imports/api/utility/TypedSimpleSchema.ts b/app/imports/api/utility/TypedSimpleSchema.ts
new file mode 100644
index 00000000..0db730c2
--- /dev/null
+++ b/app/imports/api/utility/TypedSimpleSchema.ts
@@ -0,0 +1,104 @@
+import SimpleSchema, { SimpleSchemaDefinition } from 'simpl-schema';
+
+// It DOES NOT support a constructor with multiple schemas.
+export type Definition = Exclude<SimpleSchemaDefinition, any[]>;
+
+// This is a no-op wrapper, effectively implementing a phantom type.
+export class TypedSimpleSchema<T extends Definition> extends SimpleSchema {
+  constructor(definition: T) {
+    super(definition);
+  }
+  // Extending the schema with another schema &'s their definitions
+  extend<U extends Definition>(otherSchema: TypedSimpleSchema<U>): TypedSimpleSchema<T & U> {
+    return super.extend(otherSchema);
+  }
+}
+
+// It cannot be a method due to https://github.com/microsoft/TypeScript/issues/36931.
+export function validate<T extends Definition>(schema: TypedSimpleSchema<T>, value: unknown): asserts value is InferSchema<T> {
+  schema.validate(value);
+}
+
+// If this type emerges anywhere in calculations, congratulations!
+// You've just hit an unimplemented corner case :D
+type NotImplementedMarker = { readonly NotImplementedMarker: unique symbol };
+
+// Internal calculation markers.
+type ArrayMarker = { readonly ArrayMarker: unique symbol };
+type ObjectMarker = { readonly ObjectMarker: unique symbol };
+
+export type InferType<T> = ExpandRecursively<MakeUndefinedOptional<InferTypeInner<T>>>;
+
+// Infer TypeScript type from SimpleSchema type.
+type InferTypeInner<T> =
+  T extends typeof Array ? ArrayMarker :
+  T extends typeof Boolean ? boolean :
+  // eslint-disable-next-line @typescript-eslint/ban-types
+  T extends typeof Function ? Function :
+  T extends typeof Number ? number :
+  T extends typeof Object ? ObjectMarker :
+  T extends typeof String ? string :
+  T extends RegExp ? string :
+  T extends TypedSimpleSchema<infer U> ? InferSchema<U> :
+  NotImplementedMarker;
+
+// Infer TypeScript type from a single field definition.
+export type InferField<Def extends Definition, Key extends keyof Def> =
+  Key extends string
+  ? Def[Key] extends { type: infer Typ }
+  ? ArrayMarker extends InferTypeInner<Typ>
+  ? Array<InferField<Def, `${Key}.$`>>
+  : ObjectMarker extends InferTypeInner<Typ>
+  ? { [L in keyof Def as L extends `${Key}.${infer SubKey}` ? SubKey extends `${string}.${string}` ? never : SubKey : never]: InferField<Def, L> }
+  : Def[Key] extends { allowedValues: infer Allowed extends string[] }
+  ? InferOptional<Def, Key, InferEnum<Allowed>>
+  : InferOptional<Def, Key, InferTypeInner<Typ>>
+  : NotImplementedMarker
+  : NotImplementedMarker
+
+// Infer union from string array (allowedValues should me marked as const for this to work)
+type InferEnum<T extends string[]> = T[number];
+
+// Infer optional from optional field
+type InferOptional<Def, Key extends keyof Def, U> = Def[Key] extends { optional: true } ? U | undefined : U;
+
+type MakeUndefinedOptional<Type> = { [Property in keyof Type as undefined extends Type[Property] ? never : Property]: Type[Property]; }
+  & { [Property in keyof Type as undefined extends Type[Property] ? Property : never]+?: Type[Property]; };
+
+// Infer TypeScript type from a schema definition.
+export type InferSchema<Def extends Definition> = InferField<
+  { '': { type: typeof Object } }
+  & { [Key in keyof Def as Key extends string ? `.${Key}` : never]: Def[Key] }, ''
+>;
+
+const testSchema = new TypedSimpleSchema({
+  name: {
+    type: String,
+    optional: true,
+  },
+  age: {
+    type: Number,
+  },
+  children: {
+    type: Array,
+    optional: true,
+    defaultValue: [],
+  },
+  'children.$': {
+    type: String,
+  },
+  type: {
+    type: String,
+    allowedValues: ['cat', 'dog'] as const,
+    optional: true,
+  }
+});
+
+// expands object types recursively
+type ExpandRecursively<T> = T extends object
+  ? T extends infer O ? { [K in keyof O]: ExpandRecursively<O[K]> } : never
+  : T;
+
+type testType = InferType<typeof testSchema>;
+
+type subType = ExpandRecursively<testType>
diff --git a/app/tsconfig.json b/app/tsconfig.json
index 4fdac9b5..06622c64 100644
--- a/app/tsconfig.json
+++ b/app/tsconfig.json
@@ -17,6 +17,7 @@
     "allowJs": true,
     "checkJs": true,
     "noImplicitAny": false,
+    "noErrorTruncation": true,
     "outDir": "build",
     "paths": {
       "/*": [