# building-apis

Teaches the agent how to build a Celigo API: an external system calls an HTTP endpoint, the integration runs lookups and imports, and a structured response comes back.

- 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-apis/SKILL.md
- Updated: 2026-10-23
- HTML: https://affpapa.org/en/nevibecode/skills/building-apis

## What it does

This skill covers Celigo APIs as REST endpoints that expose integration logic to outside callers. A request arrives over HTTP, moves through lookups and imports, and returns a shaped response. The agent gets the full picture of what an endpoint is made of: mode choice, request definition, processing pipeline, response routing and response shaping.

There are two modes. Builder mode is visual: a `request` with method and relative URI, `routers[]` with branches and input filters, a `responseRouter`, and `responses[]` carrying status codes and mappings. Script mode is a single `handleRequest` function that receives the method, headers without `Authorization`, `queryString`, `body` and `rawBody`, and returns `{statusCode, headers, body}`. Script mode gets no `pathParams` or `queryParams` — pick builder if your logic needs them.

One thing that trips people up: an API has no data source of its own. The request body is the record, so path params, query params and headers only reach later steps if the request `transform` writes them there. There is no schedule either, and retrying after a failure is the caller's call. Authentication is not the API's own — callers send a Celigo token with full access or one scoped to `_apiIds`. A top-level `disabled: true` takes the endpoint offline and callers get a 404 until you re-enable it.

## Install

### Claude Code (native platform)

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

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

### Codex

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

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

### Cursor

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

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

### GitHub Copilot

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

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

### Gemini CLI

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

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

### Windsurf (Devin Desktop)

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

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add celigo/ai --skill building-apis -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-apis/SKILL.md

## When to use it
- expose a lookup or write operation as a REST endpoint
- proxy a request to an external system through an authenticated connection
- return different responses depending on success or failure
- carry data from one page processor's response into the next step
- decide between visual configuration and full JavaScript control

## Example prompts
- Build a Celigo API in builder mode: a POST endpoint that takes an order and returns its id
- Write a script-mode API with a handleRequest function and custom header validation
- Configure the responseRouter so import errors go to a separate response with its own status code

## 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: 83838489d5b59bc4.

BEGIN THIRD-PARTY FILE 83838489d5b59bc4
```text
---
name: building-apis
description: Build Celigo APIs -- custom HTTP endpoints that let external systems push or query data synchronously through Celigo integrations. Use when creating APIs, proxying authenticated requests, exposing lookup/write operations as a REST interface that returns a structured response, or publishing an API to API Management.
---

<!-- TIER:1 -->

# Building APIs

An API is a **RESTful endpoint** that exposes integration logic for external consumption. External systems call the API over HTTP; the API processes the request through lookups and imports, then returns a structured response. Concerns when building an API:

- **Mode selection** -- builder (visual configuration) vs script (full JavaScript control)
- **Request definition** -- HTTP method, URI path, parameters, body schema, request transformation
- **Processing pipeline** -- routers and page processors (lookups + imports) that execute business logic
- **Response routing** -- directing processed data to the correct response definition based on success/failure or custom conditions
- **Response shaping** -- status codes, field mappings, body schema, hooks (preMap, postMap) on each response
- **Response mapping** -- extracting fields from each page processor's response back into the record for downstream steps. Configured on each `pageProcessors[]` entry, same as in flows. For lookup exports the response has `data[]` and `errors[]` (use `data[0].fieldName` for single results). For imports use `id` for the created record's ID and `_json.fieldName` for response-body fields
- **postResponseMap hook** -- JavaScript processing after response mapping, configured on `pageProcessors[]` entries

Used across integrations alongside flows and tools. APIs do not have their own authentication -- callers send a Celigo API token with full access or one scoped to the API (`_apiIds`; see [managing-api-tokens > Access Scope Decision Matrix](../managing-api-tokens/SKILL.md#access-scope-decision-matrix)) to `https://api.integrator.io/apis/{version}{relativeURI}`; outbound calls to external systems use the connections referenced by exports/imports in the pipeline.

## The Request IS the Source Record

APIs are invoked by an external HTTP caller -- there is no upstream export, no scheduler, no listener feeding them. That has three design consequences:
```
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First 2349 of 44974 bytes. © celigo · MIT · https://github.com/celigo/ai/tree/HEAD/skills/building-apis/SKILL.md

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