diff --git a/.changeset/fresh-otters-tickle.md b/.changeset/fresh-otters-tickle.md
new file mode 100644
index 00000000000..7d24416e424
--- /dev/null
+++ b/.changeset/fresh-otters-tickle.md
@@ -0,0 +1,5 @@
+---
+"@smithy/types": minor
+---
+
+add types for schemas
diff --git a/packages/types/src/command.ts b/packages/types/src/command.ts
index 101651f1ed7..fa1d2553eac 100644
--- a/packages/types/src/command.ts
+++ b/packages/types/src/command.ts
@@ -1,5 +1,6 @@
 import { Handler, MiddlewareStack } from "./middleware";
 import { MetadataBearer } from "./response";
+import { OperationSchema } from "./schema/schema";
 
 /**
  * @public
@@ -13,6 +14,8 @@ export interface Command<
 > extends CommandIO<InputType, OutputType> {
   readonly input: InputType;
   readonly middlewareStack: MiddlewareStack<InputType, OutputType>;
+  readonly schema?: OperationSchema;
+
   resolveMiddleware(
     stack: MiddlewareStack<ClientInput, ClientOutput>,
     configuration: ResolvedConfiguration,
diff --git a/packages/types/src/index.ts b/packages/types/src/index.ts
index c370335c2ab..b1dfb30b38f 100644
--- a/packages/types/src/index.ts
+++ b/packages/types/src/index.ts
@@ -21,6 +21,8 @@ export * from "./pagination";
 export * from "./profile";
 export * from "./response";
 export * from "./retry";
+export * from "./schema/schema";
+export * from "./schema/sentinels";
 export * from "./serde";
 export * from "./shapes";
 export * from "./signature";
@@ -30,6 +32,7 @@ export * from "./streaming-payload/streaming-blob-payload-input-types";
 export * from "./streaming-payload/streaming-blob-payload-output-types";
 export * from "./transfer";
 export * from "./transform/client-payload-blob-type-narrow";
+export * from "./transform/mutable";
 export * from "./transform/no-undefined";
 export * from "./transform/type-transform";
 export * from "./uri";
diff --git a/packages/types/src/schema/schema.ts b/packages/types/src/schema/schema.ts
new file mode 100644
index 00000000000..86be66ad52a
--- /dev/null
+++ b/packages/types/src/schema/schema.ts
@@ -0,0 +1,345 @@
+import type { EndpointV2 } from "../endpoint";
+import type { HandlerExecutionContext } from "../middleware";
+import type { MetadataBearer } from "../response";
+import type { EndpointBearer, SerdeFunctions } from "../serde";
+import type {
+  BigDecimalSchema,
+  BigIntegerSchema,
+  BlobSchema,
+  BooleanSchema,
+  DocumentSchema,
+  NumericSchema,
+  StreamingBlobSchema,
+  StringSchema,
+  TimestampDateTimeSchema,
+  TimestampDefaultSchema,
+  TimestampEpochSecondsSchema,
+  TimestampHttpDateSchema,
+} from "./sentinels";
+import type { TraitBitVector } from "./traits";
+
+/**
+ * A schema is an object or value that describes how to serialize/deserialize data.
+ * @public
+ */
+export type Schema =
+  | UnitSchema
+  | TraitsSchema
+  | SimpleSchema
+  | ListSchema
+  | MapSchema
+  | StructureSchema
+  | MemberSchema
+  | OperationSchema
+  | NormalizedSchema;
+
+/**
+ * Traits attached to schema objects.
+ *
+ * When this is a number, it refers to a pre-allocated
+ * trait combination that is equivalent to one of the
+ * object type's variations.
+ *
+ * @public
+ */
+export type SchemaTraits = TraitBitVector | SchemaTraitsObject;
+
+/**
+ * A schema that has traits.
+ *
+ * @public
+ */
+export interface TraitsSchema {
+  name: string;
+  traits: SchemaTraits;
+}
+
+/**
+ * Simple schemas are those corresponding to simple Smithy types.
+ * @see https://smithy.io/2.0/spec/simple-types.html
+ * @public
+ */
+export type SimpleSchema =
+  | BlobSchemas
+  | StringSchema
+  | BooleanSchema
+  | NumericSchema
+  | BigIntegerSchema
+  | BigDecimalSchema
+  | DocumentSchema
+  | TimestampSchemas
+  | number;
+
+/**
+ * Sentinel value for Timestamp schema.
+ * "Default" means unspecified and to use the protocol serializer's default format.
+ *
+ * @public
+ */
+export type TimestampSchemas =
+  | TimestampDefaultSchema
+  | TimestampDateTimeSchema
+  | TimestampHttpDateSchema
+  | TimestampEpochSecondsSchema;
+
+/**
+ * Sentinel values for Blob schema.
+ * @public
+ */
+export type BlobSchemas = BlobSchema | StreamingBlobSchema;
+
+/**
+ * Signal value for the Smithy void value. Typically used for
+ * operation input and outputs.
+ *
+ * @internal
+ */
+export type UnitSchema = "unit";
+
+/**
+ * See https://smithy.io/2.0/trait-index.html for individual definitions.
+ *
+ * @public
+ */
+export type SchemaTraitsObject = {
+  idempotent?: 1;
+  idempotencyToken?: 1;
+  sensitive?: 1;
+  sparse?: 1;
+
+  /**
+   * timestampFormat is expressed by the schema sentinel values of 4, 5, 6, and 7,
+   * and not contained in trait objects.
+   * @deprecated use schema value.
+   */
+  timestampFormat?: never;
+
+  httpLabel?: 1;
+  httpHeader?: string;
+  httpQuery?: string;
+  httpPrefixHeaders?: string;
+  httpQueryParams?: 1;
+  httpPayload?: 1;
+  /**
+   * [method, path, statusCode]
+   */
+  http?: [string, string, number];
+  httpResponseCode?: 1;
+  /**
+   * [hostPrefix]
+   */
+  endpoint?: [string];
+
+  xmlAttribute?: 1;
+  xmlName?: string;
+  /**
+   * [prefix, uri]
+   */
+  xmlNamespace?: [string, string];
+  xmlFlattened?: 1;
+  jsonName?: string;
+
+  mediaType?: string;
+  error?: "client" | "server";
+
+  [traitName: string]: unknown;
+};
+
+/**
+ * Schema for the structure aggregate type.
+ * @public
+ */
+export interface StructureSchema extends TraitsSchema {
+  name: string;
+  traits: SchemaTraits;
+  members: Record<string, [SchemaRef, SchemaTraits]>;
+}
+
+/**
+ * Schema for the list aggregate type.
+ * @public
+ */
+export interface ListSchema extends TraitsSchema {
+  name: string;
+  traits: SchemaTraits;
+  valueSchema: SchemaRef;
+}
+
+/**
+ * Schema for the map aggregate type.
+ * @public
+ */
+export interface MapSchema extends TraitsSchema {
+  name: string;
+  traits: SchemaTraits;
+  keySchema: SchemaRef;
+  valueSchema: SchemaRef;
+}
+
+/**
+ * @public
+ */
+export type MemberSchema = [SchemaRef, SchemaTraits];
+
+/**
+ * Schema for an operation.
+ *
+ * @public
+ */
+export interface OperationSchema extends TraitsSchema {
+  name: string;
+  traits: SchemaTraits;
+  input: SchemaRef;
+  output: SchemaRef;
+}
+
+/**
+ * Normalization wrapper for various schema data objects.
+ * @internal
+ */
+export interface NormalizedSchema extends TraitsSchema {
+  name: string;
+  traits: SchemaTraits;
+  getSchema(): Schema;
+  getName(): string | undefined;
+  isMemberSchema(): boolean;
+  isListSchema(): boolean;
+  isMapSchema(): boolean;
+  isStructSchema(): boolean;
+  isBlobSchema(): boolean;
+  isTimestampSchema(): boolean;
+  isStringSchema(): boolean;
+  isBooleanSchema(): boolean;
+  isNumericSchema(): boolean;
+  isBigIntegerSchema(): boolean;
+  isBigDecimalSchema(): boolean;
+  isStreaming(): boolean;
+  getMergedTraits(): SchemaTraitsObject;
+  getMemberTraits(): SchemaTraitsObject;
+  getOwnTraits(): SchemaTraitsObject;
+  /**
+   * For list/set/map.
+   */
+  getValueSchema(): NormalizedSchema;
+  /**
+   * For struct/union.
+   */
+  getMemberSchema(member: string): NormalizedSchema | undefined;
+  getMemberSchemas(): Record<string, NormalizedSchema>;
+}
+
+/**
+ * A schema "reference" is either a schema or a function that
+ * provides a schema. This is useful for lazy loading, and to allow
+ * code generation to define schema out of dependency order.
+ * @public
+ */
+export type SchemaRef = Schema | (() => Schema);
+
+/**
+ * A codec creates serializers and deserializers for some format such as JSON, XML, or CBOR.
+ *
+ * @public
+ */
+export interface Codec<S, D> extends ConfigurableSerdeContext {
+  createSerializer(): ShapeSerializer<S>;
+  createDeserializer(): ShapeDeserializer<D>;
+}
+
+/**
+ * Configuration for codecs. Different protocols may share codecs, but require different behaviors from them.
+ *
+ * @public
+ */
+export type CodecSettings = {
+  timestampFormat: {
+    /**
+     * Whether to use member timestamp format traits.
+     */
+    useTrait: boolean;
+    /**
+     * Default timestamp format.
+     */
+    default: TimestampDateTimeSchema | TimestampHttpDateSchema | TimestampEpochSecondsSchema;
+  };
+  /**
+   * Whether to use HTTP binding traits.
+   */
+  httpBindings?: boolean;
+};
+
+/**
+ * Turns a serialization into a data object.
+ * @public
+ */
+export interface ShapeDeserializer<SerializationType = Uint8Array> extends ConfigurableSerdeContext {
+  /**
+   * Optionally async.
+   */
+  read(schema: Schema, data: SerializationType): any | Promise<any>;
+}
+
+/**
+ * Turns a data object into a serialization.
+ * @public
+ */
+export interface ShapeSerializer<SerializationType = Uint8Array> extends ConfigurableSerdeContext {
+  write(schema: Schema, value: unknown): void;
+
+  flush(): SerializationType;
+}
+
+/**
+ * A client protocol defines how to convert a message (e.g. HTTP request/response) to and from a data object.
+ * @public
+ */
+export interface ClientProtocol<Request, Response> extends ConfigurableSerdeContext {
+  /**
+   * @returns the Smithy qualified shape id.
+   */
+  getShapeId(): string;
+
+  getRequestType(): { new (...args: any[]): Request };
+  getResponseType(): { new (...args: any[]): Response };
+
+  /**
+   * @returns the payload codec if the requests/responses have a symmetric format.
+   * It otherwise may return null.
+   */
+  getPayloadCodec(): Codec<any, any>;
+
+  serializeRequest<Input extends object>(
+    operationSchema: OperationSchema,
+    input: Input,
+    context: HandlerExecutionContext & SerdeFunctions & EndpointBearer
+  ): Promise<Request>;
+
+  updateServiceEndpoint(request: Request, endpoint: EndpointV2): Request;
+
+  deserializeResponse<Output extends MetadataBearer>(
+    operationSchema: OperationSchema,
+    context: HandlerExecutionContext & SerdeFunctions,
+    response: Response
+  ): Promise<Output>;
+}
+
+/**
+ * Allows a protocol, codec, or serde utility to accept the serdeContext
+ * from a client configuration or request/response handlerExecutionContext.
+ *
+ * @public
+ */
+export interface ConfigurableSerdeContext {
+  setSerdeContext(serdeContext: SerdeFunctions): void;
+}
+
+// TODO(schema): transports are not required in the current implementation.
+// /**
+//  * @public
+//  */
+// export interface Transport<Request, Response> {
+//   getRequestType(): { new (...args: any[]): Request };
+//   getResponseType(): { new (...args: any[]): Response };
+//
+//   send(context: HandlerExecutionContext, request: Request): Promise<Response>;
+// }
diff --git a/packages/types/src/schema/sentinels.ts b/packages/types/src/schema/sentinels.ts
new file mode 100644
index 00000000000..0000b9c2a29
--- /dev/null
+++ b/packages/types/src/schema/sentinels.ts
@@ -0,0 +1,79 @@
+// =============== Simple types ===================
+
+/**
+ * The blob Smithy type, in JS as Uint8Array and other representations
+ * such as Buffer, string, or Readable(Stream) depending on circumstances.
+ * @public
+ */
+export type BlobSchema = 0b0001_0101; // 21
+
+/**
+ * @public
+ */
+export type StreamingBlobSchema = 0b0010_1010; // 42
+
+/**
+ * @public
+ */
+export type BooleanSchema = 0b0000_0010; // 2
+
+/**
+ * Includes string and enum Smithy types.
+ * @public
+ */
+export type StringSchema = 0b0000_0000; // 0
+
+/**
+ * Includes all numeric Smithy types except bigInteger and bigDecimal.
+ * byte, short, integer, long, float, double, intEnum.
+ *
+ * @public
+ */
+export type NumericSchema = 0b0000_0001; // 1
+
+/**
+ * @public
+ */
+export type BigIntegerSchema = 0b0001_0001; // 17
+
+/**
+ * @public
+ */
+export type BigDecimalSchema = 0b0001_0011; // 19
+
+/**
+ * @public
+ */
+export type DocumentSchema = 0b0000_1111; // 15
+
+/**
+ * Smithy type timestamp, in JS as native Date object.
+ * @public
+ */
+export type TimestampDefaultSchema = 0b0000_0100; // 4
+/**
+ * @public
+ */
+export type TimestampDateTimeSchema = 0b0000_0101; // 5
+/**
+ * @public
+ */
+export type TimestampHttpDateSchema = 0b0000_0110; // 6
+/**
+ * @public
+ */
+export type TimestampEpochSecondsSchema = 0b0000_0111; // 7
+
+// =============== Aggregate types ===================
+
+/**
+ * Additional bit indicating the type is a list.
+ * @public
+ */
+export type ListSchemaModifier = 0b0100_0000; // 64
+
+/**
+ * Additional bit indicating the type is a map.
+ * @public
+ */
+export type MapSchemaModifier = 0b1000_0000; // 128
diff --git a/packages/types/src/schema/traits.ts b/packages/types/src/schema/traits.ts
new file mode 100644
index 00000000000..979b90b4934
--- /dev/null
+++ b/packages/types/src/schema/traits.ts
@@ -0,0 +1,55 @@
+/**
+ * A bitvector representing a traits object.
+ *
+ * Vector index to trait:
+ * 0 - httpLabel
+ * 1 - idempotent
+ * 2 - idempotencyToken
+ * 3 - sensitive
+ * 4 - httpPayload
+ * 5 - httpResponseCode
+ * 6 - httpQueryParams
+ *
+ * The singular trait values are enumerated for quick identification, but
+ * combination values are left to the `number` union type.
+ *
+ * @public
+ */
+export type TraitBitVector =
+  | HttpLabelBitMask
+  | IdempotentBitMask
+  | IdempotencyTokenBitMask
+  | SensitiveBitMask
+  | HttpPayloadBitMask
+  | HttpResponseCodeBitMask
+  | HttpQueryParamsBitMask
+  | number;
+
+/**
+ * @public
+ */
+export type HttpLabelBitMask = 1;
+/**
+ * @public
+ */
+export type IdempotentBitMask = 2;
+/**
+ * @public
+ */
+export type IdempotencyTokenBitMask = 4;
+/**
+ * @public
+ */
+export type SensitiveBitMask = 8;
+/**
+ * @public
+ */
+export type HttpPayloadBitMask = 16;
+/**
+ * @public
+ */
+export type HttpResponseCodeBitMask = 32;
+/**
+ * @public
+ */
+export type HttpQueryParamsBitMask = 64;
diff --git a/packages/types/src/serde.ts b/packages/types/src/serde.ts
index 5af727e6aab..18822f64d07 100644
--- a/packages/types/src/serde.ts
+++ b/packages/types/src/serde.ts
@@ -1,4 +1,5 @@
 import { Endpoint } from "./http";
+import { ClientProtocol } from "./schema/schema";
 import { RequestHandler } from "./transfer";
 import { Decoder, Encoder, Provider } from "./util";
 
@@ -34,6 +35,7 @@ export interface StreamCollector {
 export interface SerdeContext extends SerdeFunctions, EndpointBearer {
   requestHandler: RequestHandler<any, any>;
   disableHostPrefix: boolean;
+  protocol?: ClientProtocol<any, any>;
 }
 
 /**
diff --git a/packages/types/src/transform/mutable.ts b/packages/types/src/transform/mutable.ts
new file mode 100644
index 00000000000..5f7a47dee93
--- /dev/null
+++ b/packages/types/src/transform/mutable.ts
@@ -0,0 +1,6 @@
+/**
+ * @internal
+ */
+export type Mutable<Type> = {
+  -readonly [Property in keyof Type]: Type[Property];
+};