API Overview

The Promptly REST API lets you fetch prompts and composers directly over HTTP - no SDK required. Use it from any language or tool that can make HTTP requests.

Base URL

All API requests use the following base URL:

https://api.promptlycms.com

Authentication

Authenticate every request with a Bearer token in the Authorization header. Get your API key from the Promptly CMS dashboard.

Authorization: Bearer pk_live_...

Quick start

1. Get your API key

   Copy your API key from the dashboard settings.

2. Make your first request

   curl

   curl https://api.promptlycms.com/prompts/your-prompt-id \
     -H "Authorization: Bearer pk_live_..."

   fetch

   const response = await fetch(
     'https://api.promptlycms.com/prompts/your-prompt-id',
     {
       headers: {
         Authorization: 'Bearer pk_live_...',
       },
     },
   );
   const prompt = await response.json();

3. Use the response

   The API returns JSON with the prompt content, model configuration, and template variables:

   {
     "promptId": "your-prompt-id",
     "promptName": "My Prompt",
     "version": "1.0.0",
     "systemMessage": "You are a helpful assistant.",
     "userMessage": "Help ${name} with ${task}.",
     "config": {
       "model": "claude-sonnet-4.6",
       "temperature": 0.7,
       "schema": [],
       "inputData": null,
       "inputDataRootName": null
     }
   }

Composers

In addition to individual prompts, the API supports composers — multi-prompt workflows that combine static content with prompt segments. Fetch composers via GET /composers and GET /composers/:composerId. See the Endpoints reference for full details.

CORS

The API supports CORS for all origins. Only GET and OPTIONS methods are allowed - the API is read-only.

Performance

API responses typically return in 50-80ms, making Promptly fast enough for speed-critical applications. This means you can fetch prompts at request time rather than only at startup - your users won’t notice the overhead.

REST API vs SDK

	REST API	TypeScript SDK
Language	Any	TypeScript/JavaScript
Type safety	Manual	Automatic (with codegen)
Model resolution	Manual	Automatic (AI SDK models)
Template interpolation	Manual string replacement	Built-in userMessage() function
Best for	Non-TypeScript apps, debugging, scripting	TypeScript apps with AI SDK

Tip

If you’re building a TypeScript application, the SDK handles authentication, model resolution, and template interpolation automatically.

Next steps

• Endpoints - full reference for all API endpoints
• Rate Limits - usage quotas and rate limit headers
• Errors - error codes and troubleshooting