Capabilities

Capabilities are the core building block of ContractSpec. They define what your app can do.

Overview

A ContractSpec (or Capability) is a typed, declarative description of an operation. It defines the operation's name, version, inputs, outputs, policies, and side effects. Runtime adapters automatically serve these as REST/GraphQL/MCP endpoints with full validation and policy enforcement.

Defining a Command (Write)

import { defineCommand } from '@lssm/lib.contracts';
import { SchemaModel, ScalarTypeEnum } from '@lssm/lib.schema';

const TransferFundsInput = new SchemaModel({
  name: 'TransferFundsInput',
  fields: {
    recipient: { type: ScalarTypeEnum.NonEmptyString(), isOptional: false },
    amount: { type: ScalarTypeEnum.PositiveNumber(), isOptional: false },
  },
});

const TransferFundsOutput = new SchemaModel({
  name: 'TransferFundsOutput',
  fields: {
    transactionId: { type: ScalarTypeEnum.String(), isOptional: false },
    timestamp: { type: ScalarTypeEnum.DateTime(), isOptional: false },
  },
});

export const TransferFunds = defineCommand({
  meta: {
    name: 'wallet.transferFunds',
    version: 1,
    description: 'Transfer funds to another user',
    goal: 'Enable peer-to-peer payments',
    context: 'Requires sufficient balance',
    owners: ['team-payments'],
    tags: ['payments'],
    stability: 'stable',
  },
  io: {
    input: TransferFundsInput,
    output: TransferFundsOutput,
  },
  policy: {
    auth: 'user',
    flags: ['payments_enabled'],
  },
});

Schema Types

ContractSpec uses @lssm/lib.schema for I/O definitions. This provides Zod validation, GraphQL types, and JSON Schema from a single source.

  • • ScalarTypeEnum.NonEmptyString() - Non-empty text
  • • ScalarTypeEnum.PositiveNumber() - Positive numbers
  • • ScalarTypeEnum.DateTime() - ISO 8601 timestamps
  • • ScalarTypeEnum.Email() - Valid email addresses
  • • defineEnum(...) - Type-safe enums
Next: DataViews