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

> ## Agent Instructions
> Phaseo Gateway base URL: https://api.phaseo.app/v1. Send `Authorization: Bearer $PHASEO_API_KEY` with every request.
> Model IDs look like `provider/model`, for example `openai/gpt-6-astra`. Do not guess IDs: list them with `GET /v1/models` or check https://phaseo.app/models. `phaseo/free` routes to an available free model and needs no wallet balance.
> For new text integrations prefer `POST /v1/responses`. `POST /v1/chat/completions` (OpenAI format) and `POST /v1/messages` (Anthropic format) suit existing code.
> The full API contract is https://phaseo.app/docs/openapi/v1/openapi.yaml. Official SDKs: `@phaseo/sdk` (TypeScript) and `phaseo` (Python), plus Go, C#, PHP, Ruby and Rust.
> Search these docs over MCP at https://phaseo.app/docs/mcp, and install Phaseo skills with `npx skills add https://phaseo.app/docs`. If a page is wrong or out of date, report it with the MCP `submit_feedback` tool.
> Manage Phaseo accounts with the `phaseo` CLI (`npm install -g @phaseo/cli`, then `phaseo login` or `phaseo login --device-code`), the `/v1` Management API or the MCP server at `https://mcp.phaseo.app/mcp?access=manage`. Do not send users to the dashboard for account tasks. A person is still needed for sign-up, approving a sign-in, paying the first top-up on the checkout link that `phaseo credits add` returns when no card is saved, confirming each saved-card top-up from the emailed link, and account security (password, MFA, passkeys). Create API keys with `phaseo keys create --name <name> --json`; never guess one. Credit top-ups need `phaseo login --scopes billing:write` first. Task map: https://phaseo.app/docs/v1/developers/manage-from-an-agent.md.

# Anthropic SDK

> Use Anthropic-compatible clients with Phaseo.

Use the Anthropic-compatible API when your app, agent, or coding tool expects Claude-style `/v1/messages` requests.

## TypeScript

```bash theme={null}
npm install @anthropic-ai/sdk
```

```ts theme={null}
import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic({
	apiKey: null,
	authToken: process.env.PHASEO_API_KEY,
	baseURL: "https://api.phaseo.app",
});

const message = await client.messages.create({
	model: "anthropic/claude-sonnet-4.5",
	max_tokens: 512,
	messages: [{ role: "user", content: "Reply with only: ok" }],
});

console.log(message.content);
```

## Python

```bash theme={null}
pip install anthropic
```

```python theme={null}
import os
from anthropic import Anthropic

client = Anthropic(
    auth_token=os.environ["PHASEO_API_KEY"],
    base_url="https://api.phaseo.app",
)

message = client.messages.create(
    model="anthropic/claude-sonnet-4.5",
    max_tokens=512,
    messages=[{"role": "user", "content": "Reply with only: ok"}],
)

print(message.content)
```

## Notes

* Use the root host `https://api.phaseo.app`; Anthropic clients append `/v1/messages`.
* Pass the key as `authToken` (`auth_token` in Python), which sends `Authorization: Bearer` on every SDK version. Phaseo doesn't accept `x-api-key`, which `apiKey` sends before `@anthropic-ai/sdk` 1.0 and `anthropic` 2.0.
* `apiKey: null` stops older TypeScript SDKs from also sending your `ANTHROPIC_API_KEY`. Python SDKs before 0.98 send it whenever it is set, so upgrade or remove it from environments that call Phaseo.
* Use [Anthropic Messages](https://phaseo.app/docs/v1/api-reference/endpoint/anthropic-messages.md) for endpoint details.
* Native Anthropic tool shapes can work where Phaseo supports them, but cross-provider server tools should use Phaseo tool names.
* If a workflow depends on streamed tool loops, test it before production rollout because Anthropic-compatible clients are stricter about tool event ordering.

## Related

* [Claude Code](https://phaseo.app/docs/v1/guides/integrations/claude-code.md)
* [Anthropic Messages](https://phaseo.app/docs/v1/api-reference/endpoint/anthropic-messages.md)
* [Tool Calling](https://phaseo.app/docs/v1/guides/tool-calling.md)


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