Action Params schema — UI Protocol reference

The action DISPATCH contract: what the platform validates on the way in, and what it hands the handler on the way out.

Two halves, one surface. Inbound — action-param VALUE validation (ADR-0104 D2), below. Outbound — the runtime context an action body / handler receives: ActionSessionSchema (the ctx.session contract, #5697), ActionEngineFacade, ActionHandlerContext and ActionHandler.

Inbound — action-param VALUE validation (ADR-0104 D2)

An action's declared params[] is a complete value contract — type, required, multiple, options, reference — but before this it only informed the client dialog: the server passed reqBody.params straight to the handler, unvalidated (http-dispatcher.ts). This module is the pure contract that lets the REST and MCP dispatch paths enforce that declaration BEFORE the handler runs, reusing the D1 field value-shape contract (valueSchemaFor).

Purity: schema derivation only (Prime Directive #2). Field-backed params are resolved to their effective value-shape inputs by the CALLER (the runtime, which holds the object metadata registry); this module validates the already resolved descriptors.

TypeScript Usage

import { ActionSessionSchema } from '@objectstack/spec/ui';
import type { ActionSession } from '@objectstack/spec/ui';

// Validate data
const result = ActionSessionSchema.parse(data);

ActionSession

Action-body ctx.session — the caller identity an action body reads (runtime shape, never authored)

Properties