@zibby/skills

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The skill layer for @zibby/agent-workflow. Built-in skill definitions that give a workflow node the tools it needs — function tools, MCP servers, browser, issue trackers, memory. Vendor-neutral, JavaScript-first.

@zibby/skills is the batteries-included companion to @zibby/agent-workflow (npm) — "Graph-based AI agent workflow orchestration." The workflow engine ships zero skills on purpose; this package is where the built-in ones live.

A skill is the contract between a workflow node and a tool. It tells the engine what the tool does, how to start it, and what it needs. The engine never hardcodes any skill by name — it reads the skill definition and wires things up generically for both Claude and Cursor agents.

   @zibby/agent-workflow node            @zibby/skills
   ──────────────────────────            ─────────────
   skills: ['add']            ──►        getSkill('add')
                                           │
                                           ▼
                                         skill.resolve()  →  { command, args, env }
                                           │
                                  ┌────────┴────────┐
                                  ▼                 ▼
                              Claude SDK         Cursor CLI

---

Used with @zibby/agent-workflow

You don't use @zibby/skills on its own — it plugs into @zibby/agent-workflow. A node names the skills it wants in its skills: array, and the workflow engine resolves them at run time:

npm install @zibby/agent-workflow @zibby/skills

// 1. Import the package to register all built-in skills
import '@zibby/skills';

Define a skill once…

import { skill } from '@zibby/skills';

export const add = skill('add', {
  description: 'Add two numbers',
  input: { a: 'number', b: 'number' },
  handler: async ({ a, b }) => ({ result: a + b })
});

…and an @zibby/agent-workflow node requests it by id:

// Used by an @zibby/agent-workflow node
export const mathNode = {
  name: 'do_math',
  skills: ['add'],
  prompt: (state) => `Add ${state.a} and ${state.b}`,
};

When the engine runs do_math, it sees skills: ['add'], looks the skill up, calls resolve(), and hands the resulting tool to whichever agent runs the node. See @zibby/agent-workflow for how nodes, graphs, and state fit together.

---

Quick start

npm install @zibby/skills

Import the package to register all built-in skills:

import '@zibby/skills';

---

The skill() factory

One function to create any skill. Auto-detects the type and auto-registers.

Function skill

One skill = one tool. Flat, no nesting.

import { skill } from '@zibby/skills';

export const add = skill('add', {
  description: 'Add two numbers',
  input: { a: 'number', b: 'number' },
  handler: async ({ a, b }) => ({ result: a + b })
});

Use it in an @zibby/agent-workflow node:

export const mathNode = {
  name: 'do_math',
  skills: ['add'],
  prompt: (state) => `Add ${state.a} and ${state.b}`,
};

MCP skill

For wrapping existing MCP server packages:

import { skill } from '@zibby/skills';

export const linear = skill('linear', {
  envKeys: ['LINEAR_API_KEY'],
  description: 'Linear issue tracker',
  resolve() {
    if (!process.env.LINEAR_API_KEY) return null;
    return {
      command: 'npx',
      args: ['-y', '@modelcontextprotocol/server-linear'],
      env: { LINEAR_API_KEY: process.env.LINEAR_API_KEY },
    };
  }
});

---

Built-in skills

ID	Server	MCP Package
browser	playwright	@zibby/mcp-browser / @playwright/mcp
jira	jira	@zibby/mcp-jira
github	github	@modelcontextprotocol/server-github
slack	slack	@modelcontextprotocol/server-slack

---

Function skill API

skill(id, { description, input, handler })

• id — Unique skill identifier (used in skills: ['add'])
• description — What the tool does (shown to the LLM)
• input — Parameter definitions:

{
  param: { type: 'string' },             // full form
  other: 'number',                       // shorthand
  optional: { type: 'string', required: false },
}

• handler — The function that runs when the tool is called:

handler: async ({ param, other }) => {
  return { result: 'something' };        // any JSON-serializable value
}

Handler rules

• Must be async (or return a Promise)
• Receives one object argument with the input parameters
• Must return a JSON-serializable value
• Has full access to imports, closures, and the module scope
• Runs in a child process (the function bridge)

More examples

import { skill } from '@zibby/skills';

export const fetchUrl = skill('fetch_url', {
  description: 'Fetch a URL and return the response body',
  input: { url: 'string' },
  handler: async ({ url }) => {
    const res = await fetch(url);
    return { status: res.status, body: await res.text() };
  }
});

export const healthCheck = skill('health_check', {
  description: 'Check if the service is running',
  handler: async () => ({ status: 'ok', timestamp: Date.now() })
});

---

MCP skill API

skill(id, config)

Config object:

Property	Required	Description
resolve(options)	Yes	Returns { command, args, env } or null
serverName	No	MCP server name (defaults to id)
allowedTools	No	Tool patterns (defaults to ['mcp__<serverName>__*'])
envKeys	No	Env vars the skill needs
description	No	Human-readable description
tools	No	Tool schemas for compile-time validation
cursorKey	No	Override key in ~/.cursor/mcp.json
sessionEnvKey	No	Env var for session artifact paths (Cursor only)

Advanced example: custom binary with fallback

import { skill } from '@zibby/skills';
import { createRequire } from 'module';

const _require = createRequire(import.meta.url);

export const database = skill('database', {
  envKeys: ['DATABASE_URL'],
  description: 'Database query MCP server',
  resolve({ sessionPath } = {}) {
    let bin;
    try { bin = _require.resolve('@myorg/mcp-database/server.js'); }
    catch { bin = null; }

    if (bin) {
      return {
        command: 'node',
        args: [bin, '--read-only'],
        env: { DATABASE_URL: process.env.DATABASE_URL },
      };
    }

    return {
      command: 'npx',
      args: ['-y', '@myorg/mcp-database', '--read-only'],
      env: { DATABASE_URL: process.env.DATABASE_URL },
    };
  }
});

---

How it works under the hood

  Node definition                Skill definition              Agent strategy
  ─────────────                  ────────────────              ──────────────
  skills: ['add']        ──►     getSkill('add')        ──►    strategy-specific setup
                                   │
                                   ▼
                                 skill.resolve()
                                   │
                                   ▼
                                 { command, args, env }
                                   │
                          ┌────────┴────────┐
                          ▼                 ▼
                      Claude SDK         Cursor CLI
                      ──────────         ──────────
                      In-memory          Writes to
                      mcpServers         ~/.cursor/mcp.json
                      param to           before spawning
                      query()            `agent` CLI

Claude: The SDK receives mcpServers as a parameter. It spawns the MCP server as a child process, connects via stdio, routes tool calls through it.

Cursor: The engine writes ~/.cursor/mcp.json to disk before spawning the agent CLI. Cursor reads that file and manages MCP servers itself.

The strategies never reference any skill by name. They loop over the skill definitions and call resolve() on each.

---

API

import {
  skill,             // Unified factory — auto-detects type, auto-registers
  registerSkill,     // Register a raw skill definition
  getSkill,          // Get a skill by ID
  hasSkill,          // Check if a skill is registered
  getAllSkills,      // Get all registered skills (Map)
  listSkillIds,      // Get array of registered skill IDs
  SKILLS,            // Built-in skill ID constants
} from '@zibby/skills';

---

Companion packages

Package	What it adds
@zibby/agent-workflow	The graph engine. Skills here plug into its nodes.
@zibby/cli	zibby command — scaffold, dev server, deploy, trigger, logs.
@zibby/core	Built-in agent strategies (Claude / Cursor / Codex / Gemini / OpenAI Assistant), MCP client, runtime.

---

License

MIT