How to Get an OpenAI API Key for GPT-4o and o3
The OpenAI key itself takes about a minute. What stops people is the second half: a key with no billing behind it returns an error on the very first request, and the error does not say the word billing.
| Models you get | GPT-4.1, GPT-4o, o3, o4-mini |
|---|---|
| Key starts with | sk- |
| What it costs | Prepaid Prepaid credit. The free trial grant, where it is offered at all, expires. |
| Time to a working key | about five minutes |
| Console | platform.openai.com/api-keys |
Getting the key
- Open platform.openai.com/api-keys and sign in. The platform account is separate from the ChatGPT one even when the email is the same.
- Go to Settings, then Billing and add a payment method, then buy credit. Do this before creating the key: a key without a funded account fails on the first call, and the message it returns does not mention billing.
- Set a usage limit while you are there. The soft limit emails you, the hard limit stops the requests. Set both.
- Back on the API keys page, press Create new secret key. Give it a name and, if your account offers project scoping, put it in its own project so you can revoke it without touching anything else.
- Copy the key immediately. It starts with
sk-and is shown once. - In Calik AI, open API keys, choose OpenAI, paste and save.
Which model to start on
GPT-4o is the sensible default: fast, multimodal, cheap enough to leave running. GPT-4.1 when the instruction following has to be exact and the context is long. o3 and o4-mini are reasoning models: slower and dearer per answer, worth it on problems where the chain of thought is the product rather than the prose.
When the key does not work
OpenAI's own wording, and what each one is actually telling you.
| What you see | What it means | What to do |
|---|---|---|
insufficient_quota | Billing was never set up, or the trial grant expired. It is not a rate limit, despite reading like one. | Add a payment method in Billing and buy credit. The wording does not change until you do. |
401 Incorrect API key provided | Mistyped, revoked, or from a different organisation than the one the request names. | Recreate the key and paste it fresh. Check for a trailing space. |
429 rate_limit_exceeded | Over the requests or tokens per minute for your tier. | Wait and retry, or raise the tier by spending. Tiers move on cumulative spend and account age. |
model_not_found | Your account cannot see that model yet. New and larger models are often gated behind a spend threshold. | Pick another model from the same account, or check the limits page for what is unlocked. |
If you would rather not pay
OpenAI's own API has no standing free tier. GitHub Models is the free route that reaches a GPT class model, using a normal GitHub personal access token, at the cost of the tightest request limits on this site. The Get API page has all 27 providers with the steps for each.
Where the key goes
Calik AI never resells tokens, so the key you just created is the whole billing relationship: your prompts go from your device straight to OpenAI, and the bill is theirs to send. The key is written to your device's encrypted storage and is not copied to our servers, our database or our backups.
Open the workspace, find API keys in settings, choose OpenAI, paste and save. The model picker then lists only what your connected providers actually serve, so there is nothing in it you cannot run.
One key, then the whole workspace
48 agents, 43 AI Center modules and Agent Mesh, all driven by keys that belong to you. Free tier, no card, no expiry.
Create your account See all 27 providersQuestions people ask first
Is the OpenAI API free?
No. It runs on prepaid credit and any trial grant expires. If you want a GPT class model at no cost, GitHub Models reaches GPT-4o through a normal GitHub token, with tight request limits.
My ChatGPT Plus subscription is active. Why does my API key fail?
Because they are separate products with separate bills. The subscription covers the chat app; the API is metered against credit on your platform account. Add a payment method and buy credit in Billing, and the same key starts working.
What does insufficient_quota mean?
It means the account has no funded balance, not that you sent too many requests. It is the message OpenAI returns when billing was never set up or a trial grant ran out. Adding credit clears it.
Can I keep the key off my machine?
In Calik AI the key is written to your device's encrypted storage and nowhere else. It is not copied to our servers, our database or our backups. If you would rather nothing left the machine at all, run a local model with Ollama instead.
Can I use GPT and Claude in the same workspace?
Yes. One key per provider, both connected at once, and Agent Mesh can put them on the same question and show you where they disagree.