operations/docs/architecture/api-surface.md

status, last_updated

status	last_updated
draft	2026-04-30

API Surface

All public types, registry, call protocol, subscribe, env, validation, and adapters. See call-protocol.md for detailed call protocol semantics and adapters.md for adapter internals.

Core Types

OperationType

enum OperationType {
  QUERY = "query",
  MUTATION = "mutation",
  SUBSCRIPTION = "subscription",
}

• QUERY — read-only, no side effects
• MUTATION — write, has side effects
• SUBSCRIPTION — async generator, yields multiple values over time

Identity

interface Identity {
  id: string
  scopes: string[]
  resources?: Record<string, string[]>
}

Caller security context. scopes are global permissions (AND-checked against requiredScopes). resources maps "type:id" to action arrays (checked against resourceType/resourceAction). Derived from keypal ApiKeyMetadata.

AccessControl

type AccessControl = Static<typeof AccessControlSchema>

const AccessControlSchema = Type.Object({
  requiredScopes: Type.Array(Type.String()),
  requiredScopesAny: Type.Optional(Type.Array(Type.String())),
  resourceType: Type.Optional(Type.String()),
  resourceAction: Type.Optional(Type.String()),
  customAuth: Type.Optional(Type.String()),
})

Field	Semantics
requiredScopes	AND — caller must have ALL listed scopes
requiredScopesAny	OR — caller must have at least ONE listed scope
resourceType	Resource category for resource-scoped checks
resourceAction	Required action on the resource
customAuth	Name of custom auth function (not yet enforced)

ErrorDefinition

type ErrorDefinition = Static<typeof ErrorDefinitionSchema>

const ErrorDefinitionSchema = Type.Object({
  code: Type.String(),
  description: Type.String(),
  schema: Type.Unknown(),
  httpStatus: Type.Optional(Type.Number()),
})

Declared on IOperationDefinition.errorSchemas. Contract between operation and callers about what errors it may produce.

OperationContext

type OperationContext = Static<typeof OperationContextSchema> & {
  env?: OperationEnv
  stream?: () => AsyncIterable<unknown>
  pubsub?: unknown
}

Passed to every handler. env provides namespace-keyed access to other operations (via buildEnv). stream and pubsub support subscription and event patterns.

OperationSpec

interface OperationSpec<TInput = unknown, TOutput = unknown> {
  name: string
  namespace: string
  version: string
  type: OperationType
  title?: string
  description: string
  tags?: string[]
  inputSchema: TSchema
  outputSchema: TSchema
  errorSchemas?: ErrorDefinition[]
  accessControl: AccessControl
  _meta?: Record<string, unknown>
}

Serializable, hashable subset of an operation definition. No handler — safe to send over the wire.

IOperationDefinition

interface IOperationDefinition<TInput, TOutput, TContext> extends OperationSpec<TInput, TOutput> {
  handler: OperationHandler<TInput, TOutput, TContext> | SubscriptionHandler<TInput, TOutput, TContext>
}

Full definition including the runtime handler. Registered with OperationRegistry.

OperationHandler / SubscriptionHandler

type OperationHandler<TInput, TOutput, TContext> = (
  input: TInput, context: TContext,
) => Promise<TOutput> | TOutput

type SubscriptionHandler<TInput, TOutput, TContext> = (
  input: TInput, context: TContext,
) => AsyncGenerator<TOutput, void, unknown>

OperationHandler returns a single value. SubscriptionHandler yields values over time.

OperationEnv

type OperationEnv = Record<string, Record<string, (input: unknown) => Promise<unknown>>>

Namespace-keyed operation map. Accessed as env.namespace.operationName(input). Created by buildEnv.

Registry

OperationRegistry

Method	Signature	Description
register(operation)	(operation: IOperationDefinition) => void	Register by {namespace}.{name} key. Validates schemas.
registerAll(operations)	(operations: IOperationDefinition[]) => void	Bulk register.
get(id)	(id: string) => IOperationDefinition | undefined	Get by full id ("namespace.name").
getByName(namespace, name)	(namespace: string, name: string) => IOperationDefinition | undefined	Get by parts.
list()	() => IOperationDefinition[]	All registered operations.
getSpec(id)	(id: string) => OperationSpec | undefined	Serializable spec (no handler).
getAllSpecs()	() => OperationSpec[]	All serializable specs.
execute(operationId, input, context)	(id: string, input: TInput, ctx: OperationContext) => Promise<TOutput>	Validate input, run handler, warn on output mismatch. Throws if not found or validation fails.

Registration key format: {namespace}.{name}. Overwrite on duplicate.

execute validates input with validateOrThrow before calling the handler. Output validation uses collectErrors and logs warnings — it does not throw.

Call Protocol

PendingRequestMap

See call-protocol.md for full semantics.

Method	Signature	Description
constructor(eventTarget?)	(eventTarget?: EventTarget)	Creates internal pubsub, wires subscription handlers for responded/error/aborted.
call(operationId, input, options?)	Promise<unknown>	Publish call.requested, return Promise that resolves on call.responded.
respond(requestId, output)	void	Publish call.responded.
emitError(requestId, code, message, details?)	void	Publish call.error.
abort(requestId)	void	Publish call.aborted, reject pending Promise.
getPendingCount()	number	Number of in-flight requests.

CallHandler

type CallHandler = (event: CallRequestedEvent) => Promise<void>

Created by buildCallHandler({ registry, eventTarget? }). Subscribes to call.requested, checks access control, validates input, executes via registry. On success: no-op (handler is expected to publish call.responded through the PendingRequestMap). On failure: throws CallError.

CallEventMap

const CallEventMap = {
  "call.requested": Type.Object({ ... }),
  "call.responded": Type.Object({ ... }),
  "call.aborted": Type.Object({ ... }),
  "call.error": Type.Object({ ... }),
}

Typed event map compatible with @alkdev/pubsub. See call-protocol.md for event shapes.

Event Types

Type	Fields	Description
CallRequestedEvent	requestId, operationId, input, parentRequestId?, deadline?, identity?	Initiates a call
CallRespondedEvent	requestId, output	Successful response
CallAbortedEvent	requestId	Call cancelled
CallErrorEvent	requestId, code, message, details?	Error response

Subscribe

subscribe

function subscribe(
  registry: OperationRegistry,
  operationId: string,
  input: unknown,
  context: OperationContext,
): AsyncGenerator<unknown, void, unknown>

Direct subscription execution. Gets the operation, casts its handler to AsyncGenerator, yields each value. Properly cleans up the generator on iteration stop (calls generator.return() in finally).

This is the synchronous alternative to the call protocol's call.requested → call.responded flow for subscriptions. Use subscribe() for in-process subscription consumption; use PendingRequestMap for cross-transport subscription.

Env Builder

buildEnv

function buildEnv(options: EnvOptions): OperationEnv

interface EnvOptions {
  registry: OperationRegistry
  context: OperationContext
  allowedNamespaces?: string[]
  callMap?: PendingRequestMap
}

Creates a namespace-keyed OperationEnv for nested operation calls. Two modes:

• Direct mode: buildEnv({ registry, context }) — env functions call registry.execute()
• Call protocol mode: buildEnv({ registry, context, callMap }) — env functions call callMap.call(), publishing call.requested events with parentRequestId for call graph tracking

SUBSCRIPTION operations are filtered out — env only provides QUERY and MUTATION operations for nested calls.

allowedNamespaces restricts which namespaces are available.

Validation

Export	Signature	Description
assertIsSchema(schema, context?)	(unknown, string?) => void	Throws if schema is not a valid TypeBox schema.
validateOrThrow(schema, value, context?)	(TSchema, unknown, string?) => void	Throws with formatted errors if value fails schema check.
collectErrors(schema, value)	(TSchema, unknown) => Array<{path, message}>	Returns errors array (empty if valid).
formatValueErrors(errors, indent?)	(Iterable<{path, message}>, string?) => string	Human-readable error formatting.

Error Model

CallError

class CallError extends Error {
  readonly code: CallErrorCode
  readonly details?: unknown
  constructor(code: CallErrorCode, message: string, details?: unknown)
}

InfrastructureErrorCode

enum InfrastructureErrorCode {
  OPERATION_NOT_FOUND = "OPERATION_NOT_FOUND",
  ACCESS_DENIED = "ACCESS_DENIED",
  VALIDATION_ERROR = "VALIDATION_ERROR",
  TIMEOUT = "TIMEOUT",
  ABORTED = "ABORTED",
  EXECUTION_ERROR = "EXECUTION_ERROR",
  UNKNOWN_ERROR = "UNKNOWN_ERROR",
}

CallErrorCode is InfrastructureErrorCode | string — domain codes from errorSchemas are plain strings.

mapError

function mapError(error: unknown, errorSchemas?: { code: string; schema: unknown }[]): CallError

Converts any thrown value to CallError. If the thrown value is already a CallError, returns it. If it's an Error and errorSchemas are provided, matches against declared error codes. Falls back to EXECUTION_ERROR for unmatched Error instances and UNKNOWN_ERROR for non-Error values.

Schema Conversion

FromSchema

function FromSchema<T>(T: T): TSchema

Converts JSON Schema to TypeBox TSchema. Handles: allOf, anyOf, oneOf, enum, object (with required tracking), tuple, array, const, $ref, primitives (string, number, integer, boolean, null). Unknown shapes fall back to Type.Unknown().

Used internally by FromOpenAPI to convert OpenAPI JSON Schema definitions to TypeBox. Also used by from_mcp to convert MCP tool inputSchema (which is JSON Schema).

Adapters

See adapters.md for detailed adapter documentation.

Adapter	Import	Description
FromOpenAPI	Main barrel	OpenAPI spec → IOperationDefinition[]
FromOpenAPIFile	Main barrel	OpenAPI file → IOperationDefinition[]
FromOpenAPIUrl	Main barrel	OpenAPI URL → IOperationDefinition[]
createMCPClient	from-mcp sub-path	MCP server → MCPClientWrapper with tool operations
closeMCPClient	from-mcp sub-path	Close MCP client connection
MCPClientLoader	from-mcp sub-path	Manage multiple MCP servers
scanOperations	Main barrel	Filesystem auto-discovery of operation definitions