Glossary

Terms and definitions used in the Nellie API documentation.

A

API Key

A unique identifier used to authenticate requests to the Nellie API. API keys start with nel_ and should be kept secret. Created and managed in the Nellie dashboard.

Example: nel_abc123def456ghi789...

See also: Authentication

Asynchronous

A programming model where operations are started and completed separately. The Nellie API uses async processing; you start a job and poll for results (or receive a webhook) later.

Author

The name attributed to the generated content, appears on exported documents as the author. Set via the author parameter when creating a book. Defaults to “Nellie” if not specified. The author name can be changed for any book within the Nellie app.

B

Base URL

The root URL for all API requests.

Value: https://api.nelliewriter.com/v1

Burst Rate Limit

The maximum frequency of API requests. Currently 1 request per 6 seconds per API key.

See also: Rate Limits

C

Callback

See Webhook.

Completed

A job status indicating successful generation. When status is “completed”, the resultUrl field contains the download link.

Credits

The currency used to pay for API usage. Different operations consume different amounts of credits. Credits are pre-purchased through the Nellie app or website.

See also: Rate Limits & Credits

Custom Tone

Additional writing style guidance provided via the custom_tone parameter. Layered on top of the selected genre/style.

Example: “First-person narration, short punchy sentences, cynical wit”, or “Write like Shakespeare”

D

Daily Limit

The maximum number of requests allowed per API key per day. Currently 15 requests per 24 hours. Contact us for higher daily limits.

See also: Rate Limits

E

Endpoint

A specific URL path that accepts API requests. Each endpoint serves a specific function.

EPUB

Electronic Publication format. A standard e-book format supported by most e-readers (Kindle, Apple Books, etc.). One of the available output formats.

F

Failed

A job status indicating the generation encountered an error. Check the error field for details. Failed jobs don’t consume credits.

G

Generation

The process of creating a piece of content using Nellie AI. A single generation produces one complete book.

H

Header

HTTP header sent with API requests. The Nellie API requires:

• X-API-Key: Your API key
• Content-Type: application/json: For POST requests

HMAC-SHA256

Hash-based Message Authentication Code using SHA-256. Used to sign webhook payloads for verification.

I

Idempotent

An operation that produces the same result when applied multiple times. Webhook handlers should be idempotent to handle potential duplicate deliveries.

Images

AI-generated illustrations or photorealistic portraits included in the book. Enabled via images: true. Increases generation time.

J

Job

See Request.

JSON

JavaScript Object Notation. The data format used for API requests and responses. Also an available export format, useful for implementing Nellie generated books into your own custom apps or platforms.

M

Model

The AI system used for generation. Currently available:

• Nellie 2.0: Standard, fast, balanced performance
• Nellie 3.0: Premium, enhanced creativity, higher quality

Model Version

The model parameter value specifying which AI model to use: "2.0" or "3.0".

O

Output Format

The file format for the generated book. Options: txt, pdf, epub, md, html, json.

P

Payload

The data sent in an API request body or webhook notification body.

Polling

Repeatedly checking the status endpoint to monitor job progress. Recommended interval: every 2 minutes/120 seconds.

See also: GET /v1/status

Processing

A job status indicating active generation. Check the progress field for completion percentage.

Progress

A percentage (0-100) indicating how far along a generation job is.

Prompt

The optional text instruction describing the book to generate. Provided via the prompt parameter. Can range from a single word, to a simple concept, to a detailed outline.

Q

Queued

A job status indicating the request is waiting in the generation queue but hasn’t started processing yet.

R

Rate Limit

Restrictions on API request frequency to ensure fair usage. Two types:

• Burst: 1 request per 6 seconds
• Daily: 15 requests per day, contact us for increased limits

See also: Rate Limits

Request

A single API call to generate content. Also called a “job.” Each request has a unique requestId.

Request ID

A unique identifier (UUID) assigned to each generation request. Used to poll status and identify webhook events.

Example: abcd1234-ef56-7890-abcd-12ef34567890

Result URL

The download URL for completed generations.

Example: https://api.nelliewriter.com/v1/download/abcd1234-ef56-7890-abcd-12ef34567890

S

SDK

Software Development Kit. The official Python library for the Nellie API.

Install: pip install nellie-api

See also: SDK Reference

Signature

A cryptographic value proving webhook authenticity. Sent in the X-Nellie-Signature header.

Format: t=timestamp,v1=hmac_signature

See also: Webhooks

Status

The current state of a generation request:

• queued: Waiting in queue
• processing: Actively generating
• completed: Successfully finished
• failed: Encountered an error

Style

The genre or narrative style for generation. Unlimited options including pre-defined genres: action, comedy, drama, fantasy, horror, mystery, romance, sci_fi, thriller, etc.

See also: GET /v1/configuration

T

Timeout

The maximum time to wait for an operation:

• HTTP request: 30 seconds (configurable in SDK)
• Generation: Anywhere from 15-80 minutes
• Webhook signature: 5 minutes (for replay protection)

Type

Discrete guidance for the format/structure of generated content. Options: automatic, novel, comic, manga, childrens, non_fiction, textbook, self_help, short_story.

U

UUID

Universally Unique Identifier. A 36-character string used for request IDs.

Format: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

V

Versioning

The API uses URL path versioning. Current version: v1.

Example: https://api.nelliewriter.com/v1/book

W

Webhook

An HTTP callback that delivers results when a job completes. Alternative to polling.

Components:

• Webhook URL: Your endpoint that receives notifications
• Webhook Secret: Key for signature verification (starts with whsec_)
• Webhook Payload: JSON data about the completed job

See also: Webhooks

Webhook Secret

A secret key used to verify webhook signatures. Starts with whsec_. Found in the Nellie dashboard under Settings (user icon) > API Management > Webhooks.

Example: whsec_abc123def456...

Common Abbreviations

Related Documentation

• API Documentation: Full API reference
• FAQ: Frequently asked questions
• Quick Start: Getting started guide