diff --git a/src/entity/entity-builder.spec.ts b/src/entity/entity-builder.spec.ts
index 85e893a..5ea619a 100644
--- a/src/entity/entity-builder.spec.ts
+++ b/src/entity/entity-builder.spec.ts
@@ -1,4 +1,4 @@
-import type {IEntity} from "./entity.spec.ts";
+import type {IEntity, TTag} from "./entity.spec.ts";
 import type {TObjectProto} from "../_.spec.ts";
 
 export interface IEntityBuilder {
@@ -19,6 +19,18 @@ export interface IEntityBuilder {
      * @param component
      */
     withAll(...component: ReadonlyArray<object | TObjectProto>): IEntityBuilder
+
+    /**
+     * Add tag to target entity
+     * @param tag
+     */
+    withTag(tag: TTag): IEntityBuilder
+
+    /**
+     * Add all tags to target entity
+     * @param tags
+     */
+    withTags(...tags: ReadonlyArray<TTag>): IEntityBuilder
 }
 
 export type TEntityBuilderProto = { new(): TEntityBuilderProto };
diff --git a/src/entity/entity-builder.test.ts b/src/entity/entity-builder.test.ts
new file mode 100644
index 0000000..c1ab215
--- /dev/null
+++ b/src/entity/entity-builder.test.ts
@@ -0,0 +1,75 @@
+import {assert} from 'chai';
+import {EntityBuilder} from "./entity-builder.ts";
+import {buildWorld} from "../ecs/ecs-world.ts";
+import {createSystem} from "../system/system.ts";
+import {queryComponents} from "../ecs/ecs-query.ts";
+import {Read, WithTag, WithoutTag} from "../query/query.ts";
+
+class Component {
+    health = 100
+}
+
+const Tag = 'a-tag';
+
+describe('Test EntityBuilder', () => {
+    it('withTag', () => {
+        const entity = new EntityBuilder().withTag(Tag).build();
+
+        assert.isTrue(entity.hasTag(Tag));
+        assert.equal(entity.getTagCount(), 1);
+    });
+
+    it('withTags', () => {
+        const entity = new EntityBuilder().withTags(Tag, 'another').build();
+
+        assert.equal(entity.getTagCount(), 2);
+    });
+
+    it('deduplicates repeated tags', () => {
+        const entity = new EntityBuilder().withTag(Tag).withTag(Tag).build();
+
+        assert.equal(entity.getTagCount(), 1);
+    });
+
+    it('applies tags before the entity is handed to the world', () => {
+        let tagged = false;
+        new EntityBuilder(undefined, entity => tagged = entity.hasTag(Tag))
+            .withTag(Tag)
+            .build();
+
+        assert.isTrue(tagged);
+    });
+});
+
+describe('Tags set at build time are visible to queries', () => {
+    async function count(descriptor: Parameters<typeof queryComponents>[0], tagged: boolean) {
+        const query = queryComponents(descriptor);
+        const System = createSystem({query}).withName('Probe').withRunFunction(() => {}).build();
+        const prepWorld = buildWorld()
+            .withDefaultScheduling(root => root.addNewStage(stage => stage.addSystem(System)))
+            .withComponents(Component)
+            .build();
+        const runWorld = await prepWorld.prepareRun();
+        const builder = runWorld.buildEntity().with(new Component());
+
+        if (tagged) {
+            builder.withTag(Tag);
+        }
+
+        builder.build();
+
+        return query.resultLength;
+    }
+
+    it('WithTag matches an entity tagged by the builder', async () => {
+        assert.equal(await count({c: Read(Component), _e: WithTag(Tag)}, true), 1);
+    });
+
+    it('WithoutTag rejects an entity tagged by the builder', async () => {
+        assert.equal(await count({c: Read(Component), _e: WithoutTag(Tag)}, true), 0);
+    });
+
+    it('WithoutTag matches an entity the builder left untagged', async () => {
+        assert.equal(await count({c: Read(Component), _e: WithoutTag(Tag)}, false), 1);
+    });
+});
diff --git a/src/entity/entity-builder.ts b/src/entity/entity-builder.ts
index 1e9823e..5879862 100644
--- a/src/entity/entity-builder.ts
+++ b/src/entity/entity-builder.ts
@@ -1,4 +1,5 @@
 import {Entity, type TEntityId} from "./entity.ts";
+import type {TTag} from "./entity.spec.ts";
 import type {IEntityBuilder} from "./entity-builder.spec.ts";
 import type {TObjectProto} from "../_.spec.ts";
 
@@ -6,6 +7,7 @@ export * from './entity-builder.spec.ts';
 
 export class EntityBuilder implements IEntityBuilder {
     protected components = new Map<Readonly<object | TObjectProto>, ReadonlyArray<unknown>>();
+    protected tags = new Set<TTag>();
 
     constructor(
         protected uuid?: TEntityId,
@@ -15,11 +17,16 @@ export class EntityBuilder implements IEntityBuilder {
     build(): Entity {
         const entity = new Entity(this.uuid);
         let component;
+        let tag;
 
         for (component of this.components) {
             entity.addComponent(component[0], ...component[1]);
         }
 
+        for (tag of this.tags) {
+            entity.addTag(tag);
+        }
+
         this.callback?.(entity);
         return entity;
     }
@@ -37,4 +44,18 @@ export class EntityBuilder implements IEntityBuilder {
 
         return this;
     }
+
+    withTag(tag: TTag): EntityBuilder {
+        this.tags.add(tag);
+        return this;
+    }
+
+    withTags(...tags: ReadonlyArray<TTag>): EntityBuilder {
+        let tag;
+        for (tag of tags) {
+            this.withTag(tag);
+        }
+
+        return this;
+    }
 }
diff --git a/src/query/components-query.ts b/src/query/components-query.ts
index 12ab005..2e992e9 100644
--- a/src/query/components-query.ts
+++ b/src/query/components-query.ts
@@ -2,14 +2,15 @@ import {
     IAccessDescriptor,
     IAccessQuery,
     IComponentsQuery,
+    IExistenceDescriptor,
     TAccessQueryData,
     TAccessQueryParameter,
 } from "./query.spec.ts";
-import {EQueryType, ETargetType} from "./query.spec.ts";
+import {EExistence, EQueryType, ETargetType} from "./query.spec.ts";
 import {Query} from "./query.ts";
 import type {TObjectProto} from "../_.spec.ts";
 import type {IEntity, TTag} from "../entity/entity.spec.ts";
-import {accessDescSym, addEntitySym, entitySym} from "./_.ts";
+import {accessDescSym, addEntitySym, entitySym, existenceDescSym} from "./_.ts";
 
 export class ComponentsQuery<DESC extends IAccessQuery<TObjectProto>> extends Query<DESC, TAccessQueryData<DESC>> implements IComponentsQuery<DESC> {
     constructor(
@@ -28,7 +29,7 @@ export class ComponentsQuery<DESC extends IAccessQuery<TObjectProto>> extends Qu
         }
     }
 
-    protected getComponentDataFromEntity(entity: Readonly<IEntity>, descriptor: Readonly<DESC>): Readonly<TAccessQueryData<DESC>> {
+    protected getComponentDataFromEntity(entity: Readonly<IEntity>, descriptor: Readonly<DESC>): TAccessQueryData<DESC> {
         const components: Record<string, Readonly<object>> = {};
         let accessDesc;
         let componentDesc: Readonly<TObjectProto | TAccessQueryParameter<TObjectProto>>;
@@ -37,6 +38,10 @@ export class ComponentsQuery<DESC extends IAccessQuery<TObjectProto>> extends Qu
         for ([componentName, componentDesc] of Object.entries(descriptor)) {
             accessDesc = (componentDesc as IAccessDescriptor<object>)[accessDescSym];
 
+            if (accessDesc === undefined) {
+                continue;
+            }
+
             components[componentName] = accessDesc.targetType == ETargetType.component
                 ? (entity.getComponent(accessDesc.target as TObjectProto) ?? entity)
                 : entity;
@@ -47,9 +52,24 @@ export class ComponentsQuery<DESC extends IAccessQuery<TObjectProto>> extends Qu
 
     matchesEntity(entity: Readonly<IEntity>): boolean {
         let componentDesc: Readonly<IAccessDescriptor<TObjectProto | undefined>>;
+        let existenceDesc;
 
         // @ts-ignore todo: figure out typing. Something is still wrong somewhere
         for (componentDesc of Object.values(this.queryDescriptor)) {
+            existenceDesc = (componentDesc as Partial<IExistenceDescriptor<TObjectProto>>)[existenceDescSym];
+
+            if (existenceDesc !== undefined) {
+                const exists = existenceDesc.targetType == ETargetType.tag
+                    ? entity.hasTag(existenceDesc.target as TTag)
+                    : entity.hasComponent(existenceDesc.target as TObjectProto);
+
+                if (exists != (existenceDesc.type == EExistence.set)) {
+                    return false;
+                }
+
+                continue;
+            }
+
             if (
                 componentDesc[accessDescSym].targetType == ETargetType.tag
                 && !entity.hasTag(componentDesc[accessDescSym].target as TTag)
diff --git a/src/query/query.spec.ts b/src/query/query.spec.ts
index 9be7864..bd54bf2 100644
--- a/src/query/query.spec.ts
+++ b/src/query/query.spec.ts
@@ -3,8 +3,8 @@ import type {IEntity, TTag} from "../entity/entity.spec.ts";
 import {accessDescSym, addEntitySym, clearEntitiesSym, existenceDescSym, removeEntitySym, setEntitiesSym} from "./_.ts";
 
 export type TAccessQueryParameter<C extends TObjectProto> = C & IAccessDescriptor<InstanceType<C>>;
-export type TOptionalAccessQueryParameter<C extends TObjectProto | undefined> = IAccessDescriptor<C extends TObjectProto ? InstanceType<C> : undefined> & C extends TObjectProto ? C : undefined;
-export interface IAccessQuery<C extends TObjectProto> { [componentName: string]: TAccessQueryParameter<C> | TOptionalAccessQueryParameter<C> }
+export type TOptionalAccessQueryParameter<C extends TObjectProto | undefined> = IAccessDescriptor<C extends TObjectProto ? InstanceType<C> : undefined> & (C extends TObjectProto ? C : undefined);
+export interface IAccessQuery<C extends TObjectProto> { [componentName: string]: TAccessQueryParameter<C> | TOptionalAccessQueryParameter<C> | TExistenceQueryParameter<C> }
 
 export type TExistenceQueryParameter<C extends TObjectProto> = IExistenceDescriptor<C>;
 export type TExistenceQuery<C extends TObjectProto> = Array<TExistenceQueryParameter<C>>;
@@ -31,10 +31,13 @@ export enum EQueryType {
     Entities,
 }
 
+type TQueryParameterData<PARAM> = Required<Omit<InstanceType<PARAM & TObjectProto>, keyof IAccessDescriptor<object>>>;
+
 export type TAccessQueryData<DESC extends IAccessQuery<TObjectProto>> = {
-    [P in keyof DESC]: DESC[P] extends TAccessQueryParameter<TObjectProto>
-        ? Required<Omit<InstanceType<DESC[P]>, keyof IAccessDescriptor<object>>>
-        : (Required<Omit<InstanceType<DESC[P]>, keyof IAccessDescriptor<object>>> | undefined)
+    [P in keyof DESC as DESC[P] extends IAccessDescriptor<object | undefined> ? P : never]:
+        DESC[P] extends TAccessQueryParameter<TObjectProto>
+            ? TQueryParameterData<DESC[P]>
+            : (TQueryParameterData<DESC[P]> | undefined)
 }
 
 export type TComparator<DATA> = (a: DATA, b: DATA) => number;
diff --git a/src/query/query.test.ts b/src/query/query.test.ts
index 05fd666..19a609e 100644
--- a/src/query/query.test.ts
+++ b/src/query/query.test.ts
@@ -1,10 +1,20 @@
-import {Read, ReadEntity, Write} from "./query";
+import {Read, ReadEntity, ReadOptional, With, WithTag, Without, WithoutTag, Write} from "./query";
 import {queryComponents} from "../ecs/ecs-query";
+import {buildWorld} from "../ecs/ecs-world";
+import {createSystem} from "../system/system";
+import {Entity} from "../entity/entity";
+import {assert} from "chai";
 
 class Component {
     health = 100
 }
 
+class Marker {
+    flag = true
+}
+
+const Tag = 'a-tag';
+
 describe('Test Query', () => {
     it('pop', () => {
         const query = queryComponents({
@@ -18,3 +28,88 @@ describe('Test Query', () => {
         }
     });
 });
+
+describe('Existence parameters in component queries', () => {
+    async function count(descriptor: Parameters<typeof queryComponents>[0], tagged: boolean) {
+        const query = queryComponents(descriptor);
+        const System = createSystem({query}).withName('Probe').withRunFunction(() => {}).build();
+        const prepWorld = buildWorld()
+            .withDefaultScheduling(root => root.addNewStage(stage => stage.addSystem(System)))
+            .withComponents(Component, Marker)
+            .build();
+        const runWorld = await prepWorld.prepareRun();
+
+        const entity = new Entity();
+        entity.addComponent(new Component());
+
+        if (tagged) {
+            entity.addTag(Tag);
+        }
+
+        runWorld.addEntity(entity);
+
+        return query.resultLength;
+    }
+
+    it('With matches an entity which has the component', async () => {
+        assert.equal(await count({c: Read(Component), _e: With(Component)}, false), 1);
+    });
+
+    it('With rejects an entity which lacks the component', async () => {
+        assert.equal(await count({c: Read(Component), _e: With(Marker)}, false), 0);
+    });
+
+    it('Without rejects an entity which has the component', async () => {
+        assert.equal(await count({c: Read(Component), _e: Without(Component)}, false), 0);
+    });
+
+    it('Without matches an entity which lacks the component', async () => {
+        assert.equal(await count({c: Read(Component), _e: Without(Marker)}, false), 1);
+    });
+
+    it('WithTag matches a tagged entity', async () => {
+        assert.equal(await count({c: Read(Component), _e: WithTag(Tag)}, true), 1);
+    });
+
+    it('WithTag rejects an untagged entity', async () => {
+        assert.equal(await count({c: Read(Component), _e: WithTag(Tag)}, false), 0);
+    });
+
+    it('WithoutTag rejects a tagged entity', async () => {
+        assert.equal(await count({c: Read(Component), _e: WithoutTag(Tag)}, true), 0);
+    });
+
+    it('WithoutTag matches an untagged entity', async () => {
+        assert.equal(await count({c: Read(Component), _e: WithoutTag(Tag)}, false), 1);
+    });
+
+    it('still passes optional parameters to the system as data', async () => {
+        const query = queryComponents({c: Read(Component), o: ReadOptional(Marker)});
+        const System = createSystem({query}).withName('Probe').withRunFunction(() => {}).build();
+        const prepWorld = buildWorld()
+            .withDefaultScheduling(root => root.addNewStage(stage => stage.addSystem(System)))
+            .withComponents(Component, Marker)
+            .build();
+        const runWorld = await prepWorld.prepareRun();
+        runWorld.buildEntity().with(new Component()).build();
+
+        const first = query.getFirst()!;
+        assert.property(first, 'c');
+        assert.property(first, 'o');
+    });
+
+    it('does not pass existence parameters to the system as data', async () => {
+        const query = queryComponents({c: Read(Component), _e: Without(Marker)});
+        const System = createSystem({query}).withName('Probe').withRunFunction(() => {}).build();
+        const prepWorld = buildWorld()
+            .withDefaultScheduling(root => root.addNewStage(stage => stage.addSystem(System)))
+            .withComponents(Component, Marker)
+            .build();
+        const runWorld = await prepWorld.prepareRun();
+        runWorld.buildEntity().with(new Component()).build();
+
+        const first = query.getFirst()!;
+        assert.property(first, 'c');
+        assert.notProperty(first, '_e');
+    });
+});