> ## Documentation Index
> Fetch the complete documentation index at: https://help.slashy.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Get an Anthropic API key

> Create an Anthropic API key so you can use Claude Opus in Slashy with your own key (BYOK).

Slashy writes with Claude Sonnet by default. To use **Claude Opus** for harder drafts, you bring your own Anthropic API key — Slashy doesn't bill for Opus usage, Anthropic does. This guide walks through creating that key and adding it to Slashy.

<Note>
  You only need this if you want Opus. Sonnet works on every account with no key and no setup. See [AI models in Slashy](/features/ai-drafts/models).
</Note>

## Create the key

<Steps>
  <Step title="Sign in to the Anthropic Console">
    Go to [console.anthropic.com](https://console.anthropic.com) and sign in, or create an account if you don't have one. This is Anthropic's developer console — separate from your Claude.ai chat account.
  </Step>

  <Step title="Add billing">
    API usage is pay-as-you-go and billed by Anthropic, so the console asks you to add a payment method and some credit before keys will work. Open **Billing** (or **Plans & Billing**) and add a card or buy credits.
  </Step>

  <Step title="Open API Keys">
    Go to **Settings → API Keys** (at [console.anthropic.com/settings/keys](https://console.anthropic.com/settings/keys)).
  </Step>

  <Step title="Create a key">
    Click **Create Key**, give it a name you'll recognize later (e.g. `Slashy`), and create it.
  </Step>

  <Step title="Copy it now">
    Copy the key the moment it's shown — it starts with `sk-ant-`. Anthropic only displays the full key once; if you lose it, you'll have to create a new one.
  </Step>
</Steps>

<Warning>
  Treat the key like a password. Anyone with it can spend against your Anthropic account. Don't paste it into chats, screenshots, or shared docs.
</Warning>

## Add the key to Slashy

The first time you select Opus, Slashy prompts for the key inline in the compose window — paste it there.

<Steps>
  <Step title="Open the model picker">Click the model name above the compose box.</Step>
  <Step title="Select Opus">Choose Opus from the dropdown.</Step>
  <Step title="Paste your key">A prompt appears asking for an Anthropic API key. Paste the `sk-ant-` key and confirm. It's stored on your account only.</Step>
</Steps>

You can also add, rotate, or remove the key any time under **Settings → AI**. See [AI models in Slashy](/features/ai-drafts/models) for managing it and setting Opus as your default.

## Costs and limits

* **You pay Anthropic directly.** Opus usage is billed to the Anthropic account that owns the key, at Anthropic's published per-token rates. Slashy adds nothing on top.
* **Watch your usage** in the Anthropic Console under **Usage**. You can set spend limits there to cap monthly cost.
* **New accounts** sometimes start with a low rate limit. If Opus drafts fail with a rate-limit error, raise your limit in the console or add more credit.

## Troubleshooting

| Symptom                     | Fix                                                                                                                      |
| --------------------------- | ------------------------------------------------------------------------------------------------------------------------ |
| "Invalid API key"           | Re-copy the key from the console — it must start with `sk-ant-` and have no extra spaces. Create a fresh key if unsure.  |
| Opus fails but Sonnet works | The key is missing, wrong, or out of credit. Check **Settings → AI** in Slashy and **Billing** in the Anthropic Console. |
| Rate-limit errors           | Raise your usage tier or add credit in the Anthropic Console.                                                            |

<CardGroup cols={2}>
  <Card title="AI models in Slashy" href="/features/ai-drafts/models">When to use Sonnet vs Opus, and managing your key.</Card>
  <Card title="Customize the agent" href="/how-to-guides/customize-agent">Tune voice and instructions.</Card>
  <Card title="AI privacy" href="/getting-started/ai-privacy">How your data and BYOK requests are handled.</Card>
  <Card title="Slashy MCP" href="/features/integrations/mcp">Use Slashy's tools from Claude and other AI clients.</Card>
</CardGroup>