Connector Builder

Purpose: scaffold production-ready step commands (StepCommand) and, when truly needed, generalized I/O connectors (SpellConnector) with proper types, tests, and registration.

Read First — Companion Files

Prerequisites

• MoFlo project with cli/spells package
• TypeScript 5+
• Vitest for testing

What This Skill Does

1. Guides you through building a step command (spell step logic) or, rarely, a generalized connector (new I/O transport)
2. Generates type-safe TypeScript implementing the correct interface
3. Creates a test file with vitest mocks
4. Shows how to register the component and use it in spell YAML

Quick Start

Ask the user:

What do you want to build?

1. Step command — executes logic within a spell step (transform data, control flow, etc.)
2. Generalized connector — wraps a new I/O transport type (e.g., WebSocket, gRPC, MQTT)

Important: Simple service integrations (Slack webhook, S3 upload, Jira comment) should compose existing connectors (http, github-cli, playwright) in spell YAML — no dedicated connector needed. However, platforms requiring complex multi-step browser interaction (like Outlook.com web UI) DO warrant a dedicated connector. See ../spell-builder/architecture.md for the decision tree.

Documentation requirement: When creating any new step command or connector, you MUST also create a README.md following .claude/guidance/moflo-guidance-rules.md. Use existing READMEs in .claude/skills/spell-builder/steps/ or connectors/ as templates. Apply automatically — the user should never need to ask.

Building a Generalized Connector (Rare — New I/O Transports Only)

You almost certainly want a step command, not a connector. The three built-in connectors (http, github-cli, playwright) cover web APIs, CLI tools, and browser automation. Only create a new connector for a fundamentally new I/O transport (WebSocket, gRPC, MQTT, etc.) that no existing connector supports.

Step 1: Gather Requirements

For each action, ask:

• Action name (kebab-case)
• Description
• Input parameters (name, type, required?)
• Output fields (name, type)

Verify the connector is generalized: the name should describe an I/O transport, not a service. websocket is correct; slack is not.

Step 2: Disclose Permissions

Before generating any source, surface the connector's capability profile to the user. Capabilities like shell, fs:write, credentials, agent, net, and browser carry specific risk classifications and required warning text. See ../spell-builder/permissions.md for the levels (readonly/standard/elevated/autonomous), risk classes ([SAFE]/[SENSITIVE]/[DESTRUCTIVE]), and the warning text to display per capability.

Step 3: Generate Connector Source + Test

Use the full scaffold in templates/connector.md. It implements the SpellConnector interface with all required pieces:

• name, description, version, capabilities
• Lifecycle methods: initialize and dispose
• execute(action, params) dispatcher
• listActions() schema reporter
• Per-action validation function
• Vitest test file with mocks

The generated test file lives at src/cli/__tests__/spells/<name>.test.ts.

Step 4: Register the Connector

Add to src/cli/spells/connectors/index.ts so the engine discovers it:

import { <name>Connector } from './<name>.js';
export { <name>Connector };

export const builtinConnectors: SpellConnector[] = [
  httpConnector,
  githubCliConnector,
  playwrightConnector,
  <name>Connector,  // <-- add here
];

Step 5: Example Spell YAML

name: example-with-<name>
version: "1.0"
description: Example spell using the <name> connector

connectors:
  - <name>

steps:
  - name: do-something
    type: bash
    config:
      command: "echo 'preparing...'"

  - name: use-<name>
    type: <name>          # the step command registered in Step 4
    config:
      action: <action-1>
      # ...action params

Do not reach a connector from an agent step. That step type has never been executable. A connector is reached from its own step command (Step 4 above), from a composite step's tool action, or from a custom step command.

Building a Step Command

Step 1: Gather Requirements

Step 2: Disclose Permissions

After gathering capabilities, you MUST display the permission implications to the user — same rules as the connector path. See ../spell-builder/permissions.md for the format and per-capability warnings. Steps using destructive capabilities will require user acceptance before first run via the spell-wide dry-run report.

Step 3: Generate Step Command Source + Test

Use the full scaffold in templates/step-command.md. It implements the StepCommand<TConfig> interface with all required pieces:

• type, description, capabilities, defaultMofloLevel
• configSchema (JSONSchema for runtime validation)
• validate(config, context) and execute(config, context) methods
• describeOutputs() for downstream variable references
• Optional preflight block — see ../spell-builder/preflight.md for reason copywriting rules
• Optional rollback(config, context) for failure cleanup
• Vitest test file with mockContext

For compile-time type safety on the config, prefer the createStepCommand() factory from src/cli/spells/commands/create-step-command.ts.

Step 4: Register the Step Command

Add to src/cli/spells/commands/index.ts:

import { <type>Command } from './<type>-command.js';
export { <type>Command };
export type { <Type>StepConfig } from './<type>-command.js';

export const builtinCommands: readonly StepCommand[] = [
  agentCommand,
  bashCommand,
  // ... existing commands
  <type>Command,  // <-- add here
];

Step 5: Example Spell YAML

name: example-with-<type>
version: "1.0"
description: Example spell using the <type> step

steps:
  - name: my-step
    type: <type>
    config:
      <field1>: "value"
      <field2>: "optional-value"

Reference

Type Definitions

• Connector interface: src/cli/spells/types/spell-connector.types.ts — SpellConnector, ConnectorAction, ConnectorOutput, ConnectorCapability
• Step command interface: src/cli/spells/types/step-command.types.ts — StepCommand, StepConfig, StepOutput, CastingContext, JSONSchema
• Step factory: src/cli/spells/commands/create-step-command.ts — createStepCommand()

Existing Components

Shipped connectors (src/cli/spells/connectors/): http (http-tool.ts), github-cli (github-cli.ts), playwright (playwright.ts)

Built-in step commands (src/cli/spells/commands/): agent (agent-command.ts), bash (bash-command.ts), condition (condition-command.ts), prompt (prompt-command.ts), memory (memory-command.ts), wait (wait-command.ts), loop (loop-command.ts), browser (browser-command.ts), github (github-command.ts)

Related Skills

• /spell-builder — composes connectors and steps into spell definitions; references this skill when a needed connector doesn't exist