Write your book on your own AI key
Last checked against the product November 10, 2026
Novelmint comes with AI included: credits pay for the models that write your chapters, and you never need an account anywhere else. If you already have an API key with an AI provider, you can use that instead. Add an Anthropic, OpenAI, Google, xAI or OpenRouter key, pick any model it reaches, and your chapter builds run on it, billed by your provider. At Medium quality a build on your key costs no credits at all. You can switch between your key and Novelmint’s models for each series whenever you like.
Key takeaways
- Novelmint gives you both: AI included in your credits, or your own API key from Anthropic, OpenAI, Google, xAI or OpenRouter.
- Any model your key can reach is pickable, searched from your provider’s own list, so a model Novelmint does not run can still write your book.
- A build on your key runs the chapter’s plan, its writing and its clean-up pass on that one model. Your provider bills you, and Low and Medium builds cost no credits.
- High and Max add Novelmint’s quality judge and rewrites on top. Those run on Novelmint’s models and cost credits for that extra part only.
- Keys are checked when you save them and stored encrypted, and only the last four characters are ever shown back to you.
What it does
What your key does
Five providers
Anthropic, OpenAI, Google Gemini, xAI and OpenRouter. Through OpenRouter alone that is a long list of models from many makers.
Any model the key reaches
Once a key is saved, the AI Models tab lists the models your provider offers you, with the provider’s own prices where it publishes them. Search, pick one, and it writes the series.
The whole build on one model
The plan for each beat, the prose and the clean-up pass all run on the model you picked, so the chapter reads in its voice from first line to last.
No credits at Medium
Your provider bills your account for what the model writes. A Low or Medium build on your key costs no Novelmint credits.
High and Max still available
Pick High or Max and Novelmint adds its judge and rewrites on top of your model’s draft. You pay credits only for that extra, and the estimate shows it before you start.
Per series, or for everything
Set a key model on one series, or as your Studio default so every series without models of its own uses it. One click puts a series back on Novelmint’s models, and your earlier picks are still there.
How to use it
From key to chapter
Add your key
Open Account, then AI keys. Paste a key from any of the five providers and save. Novelmint checks it with your provider first, and a key the provider refuses is not saved.
Open a series’ AI Models tab
Under "Build on your own key", the models your keys reach load in a searchable list. For every series at once, use the AI Models tab in your Studio instead.
Pick a model
Choose one. The tab confirms that builds in this series now run on it. Not sure which? Try a few side by side on the Bake-off tab first.
Build as usual
Press Build on a chapter. The estimate reflects your key: nothing in credits at Low or Medium, only the extra at High or Max.
If the key stops working
A revoked key or an empty balance pauses the build with your provider’s message. Fix it under AI keys and press Build again. Novelmint never quietly switches to its own models behind your back.
Questions
Frequently asked
- Can I use my own API key with Novelmint?
- Yes. Add an Anthropic, OpenAI, Google, xAI or OpenRouter key under Account, then AI keys, and pick a model from it on a series’ AI Models tab. Chapter builds in that series then run on your key and your provider bills you directly.
- Do I need my own key to use Novelmint?
- No. AI is included: credits pay for Novelmint’s models, and you can write and publish a whole book without an account at any AI provider. Your own key is an option for authors who want it, and each series can use one or the other.Pricing
- Does building on my own key cost credits?
- At Low and Medium quality, no: the plan, the writing and the clean-up pass all run on your key. High and Max add Novelmint’s quality judge and rewrites, which run on Novelmint’s models, so those levels cost credits for that extra part only. The build estimate shows the figure before you start.Pricing
- Which models can I use?
- Any model your key can reach. Novelmint asks your provider for the list of models available to you and lets you search it. An OpenRouter key opens models from many makers through one account.
- How is my key kept safe?
- Novelmint checks each key with your provider when you save it, stores it encrypted, and only ever shows its last four characters. You can replace or remove a key at any time from the same page.
- Does my key pay for everything?
- Only chapter builds. Minty, audio narration, translations and covers always run on Novelmint and use credits as usual.
- What happens to my writing on my provider’s side?
- The prompts for a build go to your provider under your account, so your provider’s terms apply. Some providers keep a log of requests; for OpenAI, Novelmint asks that requests not be stored.
- Can I pick a different model for one beat while on my key?
- Not while a key model is set. A build on your key writes every beat with that one model, so the chapter reads in one voice. Switch the series back to Novelmint’s models to choose models per beat.Choose your AI model
What this page does not claim
- It does not make a build free at High or Max. Those levels add Novelmint’s judge and rewrites, which cost credits.
- Your key pays for chapter builds only, not for Minty, narration, translation or covers.
- It does not control what your AI provider charges or keeps. Their prices and terms are between you and them.
- It does not fall back to Novelmint’s models when your key fails. The build pauses until you fix the key or switch the series back. At High or Max, judging already done before the key failed is charged.
- Free Low and Medium builds are the ones you start yourself. A build run by an AI agent may add a small charge for filling in empty beat notes.
Keep reading
Choosing the model, and testing it first
Your key is one way to pick the AI that writes your book. The same AI Models tab picks among Novelmint’s own measured models, and the Bake-off tab lets you try several on the same scenes before you commit.
Related
Plan a book with Minty
Talk the story through and watch it become chapters and scenes on your Timeline.
Chapter builds
Turn a chapter’s beats into prose, written from your plan, your bible, and your voice.
Choose your AI model
Pick the AI model that writes your series, compared on measured writing quality and cost, and pin a different one to any single beat.
Model bake-off
Run our fiction benchmark on up to five AI models, ours or ones on your own key, and read their scenes side by side with blind judges’ scores.
Use the AI you already pay for, or the AI that comes included.
No card. Your first chapter is free.