API Reference

The FetchPrompt REST API lets you fetch prompt content at runtime from any application. All endpoints are served from the Edge for low latency worldwide.

Base URL: https://www.fetchprompt.com/api/v1

Authentication

All API requests require a Bearer token in the Authorization header:

Authorization: Bearer fp_prod_your_key_here

The API key determines both the organization and environment (Stage or Production) for the request. See API Keys for details on creating and managing keys.

Endpoints

List all prompts

Returns all prompts for the organization and environment associated with your API key.

GET /api/v1/prompts

Headers:

Response 200 OK:

{
  "data": [
    {
      "slug": "customer-support-bot",
      "name": "Customer Support Bot",
      "version": 3,
      "environment": "prod",
      "updated_at": "2026-02-24T10:30:00Z"
    },
    {
      "slug": "email-subject-generator",
      "name": "Email Subject Generator",
      "version": 1,
      "environment": "prod",
      "updated_at": "2026-02-23T15:00:00Z"
    }
  ]
}

Prompts are ordered by updated_at (most recently updated first).

Fetch a prompt (GET)

Fetches a single prompt by slug. Supports variable interpolation via query parameters and ETag caching.

GET /api/v1/prompts/{slug}

Path parameters:

Query parameters (optional):

Any query parameter is treated as a variable for interpolation. For example:

GET /api/v1/prompts/my-prompt?user_name=Sarah&tone=friendly

This replaces {{user_name}} with Sarah and {{tone}} with friendly in the prompt content.

Headers:

Response 200 OK:

{
  "slug": "customer-support-bot",
  "name": "Customer Support Bot",
  "content": "You are a helpful customer support agent. The customer's name is Sarah.",
  "version": 3,
  "environment": "prod"
}

If some variables in the prompt were not provided, the response includes a missing_variables field:

{
  "slug": "customer-support-bot",
  "name": "Customer Support Bot",
  "content": "You are a helpful customer support agent for {{company_name}}. The customer's name is Sarah.",
  "version": 3,
  "environment": "prod",
  "missing_variables": ["company_name"]
}

Response 304 Not Modified:

Returned when the If-None-Match header matches the current ETag. No body is returned.

Response headers:

Render a prompt (POST)

Fetches a prompt and renders it with variables provided in a JSON body. Use this when you have many variables or values that contain special characters.

POST /api/v1/prompts/{slug}

Path parameters:

Headers:

Request body:

{
  "user_name": "Sarah",
  "company_name": "Acme Inc",
  "tone": "friendly"
}

Pass variables as a flat JSON object. The body is optional — if omitted or empty, the prompt content is returned without interpolation.

Response 200 OK:

{
  "slug": "customer-support-bot",
  "name": "Customer Support Bot",
  "content": "You are a helpful customer support agent for Acme Inc. The customer's name is Sarah. Respond in a friendly tone.",
  "version": 3,
  "environment": "prod"
}

If some variables in the prompt were not provided, the response includes a missing_variables field:

{
  "slug": "customer-support-bot",
  "name": "Customer Support Bot",
  "content": "You are a helpful customer support agent for {{company_name}}. The customer's name is Sarah. Respond in a friendly tone.",
  "version": 3,
  "environment": "prod",
  "missing_variables": ["company_name"]
}

Response 304 Not Modified:

Returned when the If-None-Match header matches the current ETag. No body is returned.

Response headers:

Error responses

All error responses follow this format:

{
  "error": "Error message describing what went wrong"
}

Code examples