What is an API Key?
An API Key acts as a secure, private password. It connects the local tools running in your browser to model providers (like Google, OpenAI, or Anthropic). It authenticates your session and tells the provider which account to charge for processing.
How do Credits Work?
Instead of paying a flat $20/month subscription, API access is strictly pay-as-you-go. You pre-load your developer account with a small balance ($5 to $10), and the provider deducts fractions of a cent per request based on the tokens processed.
What is a Token?
AI models do not measure text in words; they measure in tokens (chunks of characters). As a rule of thumb, 1,000 tokens is approximately 750 words. An average chapter of 3,000 words equals roughly 4,000 tokens.
Supported Model Providers
Detailed specifications, active 2026 pricing, and step-by-step setup links for each console.
Gemini AI Studio
Best all-rounder with a generous free tier and massive manuscript context support.
| Model | Input / 1M | Output / 1M |
|---|---|---|
| Gemini 3.5 Flash | $1.50 | $9.00 |
| Gemini 3.1 Pro | $2.00 | $12.00 |
| Gemini 3 Flash | $0.50 | $3.00 |
| Gemini 2.5 Flash | $0.30 | $2.50 |
Setup Instructions
- Navigate to Google AI Studio.
- Log in with your Google account.
- Click "Get API Key" in the top left panel.
- Select "Create API Key" and copy the generated key.
- Optional: Set up billing for unlimited, high-speed rate limits.
OpenAI Developer
The industry benchmark. The mini model family offers incredible cost efficiency.
| Model | Input / 1M | Output / 1M |
|---|---|---|
| GPT-4o | $2.50 | $10.00 |
| GPT-4o-mini | $0.15 | $0.60 |
Setup Instructions
- Navigate to the OpenAI Platform.
- Register an account and log in.
- Go to Settings > Billing and select "Add Funds" (min. $5).
- Turn off auto-recharge to maintain strict budget limits.
- Go to "API Keys", click "Create new secret key", and save it.
Claude Console
Praised by novelists for prose generation, editing, and capturing character voice.
| Model | Input / 1M | Output / 1M |
|---|---|---|
| Claude 4.6 Sonnet | $3.00 | $15.00 |
| Claude 4.5 Haiku | $1.00 | $5.00 |
| Claude 4.7 Opus | $5.00 | $25.00 |
Setup Instructions
- Navigate to the Anthropic Console.
- Create a developer account.
- Click the "Billing" tab and fund your account (min. $5).
- Navigate to the "API Keys" tab.
- Select "Create Key", copy it immediately, and keep it safe.
GroqCloud
Blazing fast open-source Llama model hosting. Great for brainstorming and outlines.
| Model | Input / 1M | Output / 1M |
|---|---|---|
| Llama 3.3 70B | $0.59 | $0.79 |
| Llama 3.1 8B | $0.05 | $0.08 |
Setup Instructions
- Navigate to the Groq Console.
- Log in and accept developer agreements.
- Go to the "API Keys" section in the sidebar.
- Click "Create API Key" and copy it.
- Utilize the free-tier rate limits, or add billing to scale capacity.
OpenRouter Console
A single dashboard and API key to access any model from Google, OpenAI, Anthropic, and more.
| Details | Rate Structure |
|---|---|
| Inference Rates | Passthrough (Same as provider native) |
| Payment Fee | 5.5% on top-ups ($0.80 minimum) |
| Free Tier | A variety of high-quality free models |
Setup Instructions
- Navigate to the OpenRouter Console.
- Create an account.
- Go to Account > Credits and fund your balance (min. $10).
- Navigate to the "Keys" section in your dashboard.
- Click "Create Key" and save the key generated.
Manuscript API Cost Estimator
Estimate the exact cost of running outlines, edits, or developmental reports on your text.
API Billing FAQ
Will my card automatically be charged?
No. For OpenAI, Claude, and OpenRouter, you must explicitly pre-purchase developer credits. Once your credit balance reaches zero, the API simply stops responding until you add more funds. Your credit card is not charged automatically unless you choose to turn on "auto-recharge."
Does my data train the AI models?
No. One of the greatest benefits of developer API accounts (unlike ChatGPT Plus or Claude.ai consumer accounts) is that all major providers explicitly state in their developer terms of service that data submitted via the API is never used to train models. Your intellectual property remains completely secure.
Do API credits expire?
It depends on the provider. OpenAI and Claude credits typically have an expiration window of 12 months from purchase. OpenRouter credits do not expire. Google Gemini's pay-as-you-go billing functions as a post-paid monthly invoice, so you are billed at the end of the month only for what you consumed.
Why is my API key failing or throwing a 401 error?
A 401/403 or "Authentication Error" usually means one of three things: (1) there is a typo in the key you pasted, (2) you created a key but have not pre-loaded funds onto that developer account, or (3) your developer account is under review or blocked. Always test with Gemini's free tier if you need to isolate billing issues.