# building-tools

A skill for building reusable Celigo tool resources: lookups, imports, transforms and branching behind one input/output contract.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 2900 installs · ★ 4
- Author: celigo
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/celigo/ai/tree/HEAD/skills/building-tools/SKILL.md
- Updated: 2026-10-23
- HTML: https://affpapa.org/en/nevibecode/skills/building-tools

## What it does

This skill covers how to build a Celigo tool — a reusable block that hides lookups, imports, transforms and branching behind a defined input and output contract. Build it once, then call it from flows, APIs, AI agents, MCP servers and other tools.

The build order is laid out: connection first, then export and import, then the tool itself, then the consumer (flow, API, agent or MCP server). It walks through the architecture — `input` as a JSON Schema, `routers[]` holding branches, `pageProcessors[]` holding lookups and imports, and `output` with its schema and mappings. There is also a clear split between a tool, an API and a flow, and an explanation of why a tool never starts itself: no `schedule`, no listeners.

Connections are bring-your-own-keys. The caller maps connections to the tool at configuration time, and an MCP server can swap them per-server without touching the tool. If the logic belongs to a single flow and won't be reused, skip the tool and inline the processor instead. Worth checking how many consumers your logic actually has before creating a separate resource.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add celigo/ai --skill building-tools -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/building-tools/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/building-tools/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add celigo/ai --skill building-tools -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/building-tools/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add celigo/ai --skill building-tools -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/building-tools/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install celigo/ai building-tools
```

2. **Manually: put the files in place**
- File: `.github/skills/building-tools/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add celigo/ai --skill building-tools -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/celigo/ai --path skills/building-tools
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/building-tools/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add celigo/ai --skill building-tools -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/celigo/ai/tree/HEAD/skills/building-tools/SKILL.md

## When to use it
- wrap a lookup, import and branch into one reusable block
- call the same logic from a flow, an API and an AI agent
- publish logic as an MCP server endpoint
- swap connections per consumer without editing the tool
- nest one tool inside another for composed orchestration

## Example prompts
- Build a tool that looks up a customer in NetSuite by email and imports an order
- Describe the input and output contract for a new tool
- How do I chain two tools with nextRouterId?

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 32126f17e4f25b34.

BEGIN THIRD-PARTY FILE 32126f17e4f25b34
````text
---
name: building-tools
description: Build Celigo tool resources -- reusable building blocks that encapsulate lookups, imports, transforms, and branching behind input/output contracts. Callable from flows, APIs, AI agents, MCP servers, and other tools. Use when creating tools, adding steps, or configuring routing.
---

<!-- TIER:1 -->

# Building Tools

A tool is Celigo's **first-class reusable building block**. It encapsulates logic -- lookups, imports, transforms, branching -- behind a defined input and output contract. Build it once, use it everywhere: from Flows, APIs, AI Agents, MCP Servers, and other Tools.

## Tool Concepts

**Why tools exist:** Without tools, users build the same lookup-transform-import patterns repeatedly across Flows, APIs, and Agents. Tools solve this by providing a governed, composable abstraction: one definition, many consumers, consistent behavior.

**When to build a tool:**

- You're building an **MCP server** -- MCP servers expose tools as endpoints; every piece of logic an MCP server offers must be a tool
- The same logic is needed by **2+ consumers** (flows, APIs, agents, MCP servers) -- build once, call everywhere
- You want **connection flexibility** -- callers can pass different connections to the same tool definition
- You're **composing smaller pieces** -- tools can call other tools for nested orchestration

**When NOT to build a tool:**

- The logic is **specific to one flow or API and won't be reused** -- inline it as a lookup/import processor directly
- You need **abstract/instance templating** for multi-tenant patterns -- use abstract flows

**Tool vs API:** the split is the contract callers get. A **tool** is called by flow steps, AI agents, APIs and other tools, and outside callers can reach it too: a caller authenticated to the Celigo REST API can run it directly through its invoke operation (input plus connection bindings; the output comes back synchronously), and an MCP server publishes tools to outside AI clients. Put an **API** in front only when callers need their own URL, method and status codes (a partner system, a customer-facing app) -- the tool stays available to its other consumers at the same time.

**Tool vs flow:** tools don't start themselves -- no `schedule`, no listeners, no flow-level runtime controls, and no abstract/instance layer (a tool is already the unit of reuse; per-environment variation is handled by the consumer-bound connection model). A step's own `proceedOnFailure` is set on its page-processor entry, as in a flow ([step 7](#7-wire-page-processors-into-branches)). "Every night, do X" or "when a webhook arrives, do Y" is a flow -- the tool may be the thing the flow *does*.

**Architecture:**

```
Tool
+-- input         -- JSON Schema defining what callers send
````
END THIRD-PARTY FILE 32126f17e4f25b34

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