How to Get a Claude API Key (Anthropic)
Claude runs on prepaid credit rather than a free tier, which is the one thing most guides leave out until you are already three steps in. Here is the whole route, including the part where you pay, and the mistakes that cost people an afternoon.
| Models you get | Claude Opus 5, Claude Fable 5, Claude Sonnet 5, Claude Haiku 4.5 |
|---|---|
| Key starts with | sk-ant- |
| What it costs | Prepaid Prepaid credit. No free tier, and the smallest top up is a few dollars. |
| Time to a working key | about ten minutes, five of them phone verification |
| Console | platform.claude.com/settings/keys |
Getting the key
- Open platform.claude.com and sign up with an email address or a Google account. This is the developer console. It is a different product from the Claude chat app, and the old address console.anthropic.com now redirects here.
- Verify your phone number when it asks. Anthropic uses it to stop one person opening many accounts, and no key can be created until it is done.
- Go to Plans & Billing, add a payment method and buy credit. The Claude API has no free tier: it runs on a prepaid balance. That balance is the only thing you ever pay for, and you pay it to Anthropic.
- While you are in billing, set a monthly spend limit. It is the one setting that turns an API key from an open tap into a budget, and it takes one click.
- Open Settings, then API keys, and press Create Key. Name it something you will recognise later, such as
calik-ai, and leave the workspace on Default. - Copy the key the moment it appears. It starts with
sk-ant-and the console shows the full value exactly once. If you lose it, delete that key and make another; it costs nothing. - In Calik AI, open API keys, choose Anthropic, paste and save. The model picker fills with Opus 5, Fable 5, Sonnet 5 and Haiku 4.5 straight away.
Which model to start on
Haiku 4.5 for volume work, classification and quick drafts: cheapest per token by a wide margin. Sonnet 5 is the sensible default for everyday work. Opus 5 for problems where a wrong answer costs more than the tokens do, which in practice means long refactors, architecture calls and anything you would otherwise check by hand. Switch per conversation, so the expensive model is only in the room when it needs to be.
When the key does not work
Claude's own wording, and what each one is actually telling you.
| What you see | What it means | What to do |
|---|---|---|
credit balance is too low | The prepaid balance ran out, or was never added. | Top up in Plans and Billing. Nothing on our side is involved. |
401 invalid x-api-key | The key is mistyped, revoked, or you pasted a claude.ai session token. | Copy it again from the console and check it starts with sk-ant-. Watch for a trailing space. |
429 rate_limit_error | Over the requests or tokens per minute your usage tier allows. | Anthropic raises the tier automatically as cumulative spend passes each threshold. Pace the run or wait. |
529 overloaded_error | Anthropic is saturated. Nothing to do with your key. | Retry shortly, or send the question to a second provider you have connected. |
If you would rather not pay
Claude has no free API tier at all. If the budget is the blocker, the closest free routes are GitHub Models, which reaches a GPT class model, and Google AI Studio, which reaches Gemini 2.5 Pro. 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 Anthropic, 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 Claude, 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 Claude API free?
No. Anthropic runs it on prepaid credit, so you add a payment method and buy a balance before the first request. There is no free tier and no trial clock. The free routes on this site are Google AI Studio, Groq, GitHub Models, OpenRouter's free models and running a model locally with Ollama.
I already pay for Claude Pro. Can I use that key?
There is no key to use. Claude Pro is a subscription to the claude.ai chat app and the API is billed separately on prepaid credit. Neither includes the other. You need a key created at platform.claude.com, starting with sk-ant-.
How much will a Claude API key cost me?
It depends entirely on which model and how much text, which is why no figure is printed here: rates move and a stale number is worse than none. Anthropic's pricing page carries the current per token rates. The practical control is yours: set a monthly spend limit, keep Haiku 4.5 for volume and bring Opus 5 in only where being wrong is expensive.
Where is my Claude API key stored in Calik AI?
In your device's encrypted storage, and nowhere else. It is not copied to our servers, it is not in our database and it is not in our backups. Prompts travel from your device to Anthropic without passing through us.
Can I use Claude alongside GPT and Gemini?
Yes, and it is the setup we would recommend. Calik AI keeps one key per provider and they do not interfere. Agent Mesh then puts models from different providers on the same question, so you get two or three independent readings and the points where they disagree.