# Base URLs

> The one setting that trips everyone up: which URL each client expects, with and without the /v1 suffix.

_Source: https://aiprimetech.io/docs/getting-started/base-urls/ · Home > Docs > Getting started_

Almost every failed integration is a base-URL mistake. This page is the reference for exactly what to set.


## The rule

| Client | Set base URL to | Then it calls |
|---|---|---|
| Anthropic SDK (Python / TS) | `https://aiprimetech.io` | `https://aiprimetech.io/v1/messages` |
| Claude Code | `https://aiprimetech.io` | `https://aiprimetech.io/v1/messages` |
| OpenAI SDK (Python / TS) | `https://aiprimetech.io/v1` | `https://aiprimetech.io/v1/chat/completions` |
| LangChain / LiteLLM / Cursor | `https://aiprimetech.io/v1` | `https://aiprimetech.io/v1/chat/completions` |

> **Anthropic clients: no `/v1`. OpenAI clients: with `/v1`.** The Anthropic SDK appends `/v1/messages` to whatever base you give it; the OpenAI SDK appends only `/chat/completions`. Adding `/v1` to an Anthropic base produces requests to `/v1/v1/messages`, which 404s.


## How to tell which mistake you made

| You see | Meaning |
|---|---|
| `404` and the path contains `/v1/v1/` | You added `/v1` to an Anthropic-style base URL. Remove it. |
| `404` on `/chat/completions` with no `/v1` | You omitted `/v1` from an OpenAI-style base URL. Add it. |
| `404` on `/v1/chat/completions` from an Anthropic tool | The tool speaks Messages, not Chat Completions. Use the Anthropic base and endpoint. |
| Connection works but every call 401s | Right URL, wrong auth header for that format. See [Authentication](/docs/getting-started/authentication/). |


## Verifying without any SDK

This is the fastest way to prove the URL and key are right before blaming your framework:

```bash
# should return JSON with a "data" array of model ids
curl -s -o /dev/null -w "%{http_code}\n" https://aiprimetech.io/v1/models \
  -H "Authorization: Bearer $CLAUDEAPIKEY"
```

A `200` means URL and key are both correct, and any remaining problem is in your client configuration.

- [Authentication](https://aiprimetech.io/docs/getting-started/authentication/) — Headers and env vars
- [Troubleshooting](https://aiprimetech.io/docs/guides/troubleshooting/) — Symptom-first debugging
- [Overview](https://aiprimetech.io/docs/api-reference/overview/) — Endpoint reference


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_ClaudeAPIKey.dev is an independently operated, Anthropic-compatible API gateway. Not affiliated with Anthropic._