# Move from the Anthropic API The exchange serves `POST /v1/messages` in the Anthropic format. The official clients work with a new base URL and a new key. Server tools and the batch and file endpoints need more work. For setup, see [Anthropic SDK](https://inference.ai.exchange/docs/connect-anthropic-sdk.md) and [Claude Code](https://inference.ai.exchange/docs/connect-claude-code.md). ## Change these three things 1. Issue a `spend` key on the **API keys** page. See [API keys](https://inference.ai.exchange/docs/keys.md). 2. Set the base URL to `https://router.inference.ai.exchange`, with no `/v1`. The client adds `/v1/messages`, so a URL that ends in `/v1` gets a 404. 3. Change each `model` to a name that `GET /v1/anthropic/models` lists. See [Model names](#model-names). Then check these: - Keep `max_tokens` in each request. The exchange requires it. - Remove each server tool. See [Anthropic features](#anthropic-features). - Run a [dry run](https://inference.ai.exchange/docs/move-from-openrouter.md#check-a-request-without-a-purchase). - Read [What is different about money](https://inference.ai.exchange/docs/move-from-openrouter.md#what-is-different-about-money). The exchange never lowers `max_tokens` to fit your balance or cap. ## What differs - **Model names.** The exchange does not forward a Claude name to one provider. An unknown name returns `404 model_not_found`. - **Server tools.** `web_search_*`, `web_fetch`, `code_execution` and other hosted tools return `400 unsupported_parameter`. To search the web, add `:web` (beta) to the model name. - **Documents.** A `document` block must have a `base64` source. A `url` source returns `400 unsupported_content`. - **Not available.** The Message Batches API and the Files API. ## Example An Anthropic request, then the same request for the exchange. The new request changes the client and model, removes the refused `web_search` tool and adds a cap. The model name is an illustration. ```python import anthropic client = anthropic.Anthropic() message = client.messages.create( model="claude-sonnet-4-6", max_tokens=1024, system="Answer in one sentence.", messages=[{"role": "user", "content": "What is new in Rust?"}], tools=[{"type": "web_search_20260209", "name": "web_search"}], metadata={"user_id": "user-123"}, ) ``` ```python import os import anthropic client = anthropic.Anthropic( base_url="https://router.inference.ai.exchange", api_key=os.environ["LIQUID_API_KEY"], ) message = client.messages.create( model="liquid.auto", max_tokens=1024, system="Answer in one sentence.", messages=[{"role": "user", "content": "What is new in Rust?"}], metadata={"user_id": "user-123"}, extra_body={"exchange": {"cap_usd": 0.05}}, ) ``` ## Reference ### Settings that change - Both `x-api-key` and `Authorization: Bearer` work with an exchange key, `sk-liquid-…`. - `anthropic-version` is accepted and not required. On `GET /v1/models`, it selects the Anthropic format. - `anthropic-beta` is accepted and not read. - `max_tokens` is required. The exchange can lower it to the limit of the offers that can take the job. See [Output limits](https://inference.ai.exchange/docs/errors.md#output-limits). ### Model names Send a name that `GET /v1/anthropic/models` returns, a router model, a basket or a preset. See [Connect an app](https://inference.ai.exchange/docs/connect-overview.md). An unknown name returns `404 model_not_found`. The exchange never uses a different model. Send the `exchange` object in the body. See [Purchasing rules](https://inference.ai.exchange/docs/rules.md). ### Anthropic features | Anthropic feature | What the exchange does | | --------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `system` (a string or a list of blocks) | Applied. It becomes the first message. | | `stream` | Applied, in the Anthropic event format. The final event has the `exchange` block. | | `stop_sequences`, `temperature` | Applied. An offer must support `stop_sequences` to compete. | | `top_p`, `top_k` | Passed to a provider that declares support. If no offer supports it, `unsupported_parameter`. | | `metadata.user_id` | Names the end user for the limits of a [guardrail](https://inference.ai.exchange/docs/guardrails.md#end-users). | | `service_tier`, `container`, any parameter not in this table | Ignored or accepted and not sent. To label spend, send `x-liquid-tag`. See [Cost tags](https://inference.ai.exchange/docs/rules.md#cost-tags). | | `tools` with an `input_schema`, and `tool_choice` | Applied. Types `auto`, `any`, `tool` and `none` work. `disable_parallel_tool_use` is not read. Only an offer that declares tool support can win. | | Typed client tools `bash`, `text_editor`, `computer`, `memory` | Applied as functions. Your client runs the tool. A tool with no `input_schema` gets an empty object schema, so declare your own. | | Server tool `web_search_*` | `400 unsupported_parameter`, `param` such as `tools[0]`. Add `:web` (beta) to the model name instead. See [Quickstart](https://inference.ai.exchange/docs/quickstart.md#web-access). | | Other typed tools: `web_fetch`, `code_execution`, `tool_search` | `400 unsupported_parameter`. The exchange runs no hosted tool. Run the work in your own code. | | `thinking` with `budget_tokens` | Applied as a reasoning budget. Only an offer that supports a budget can win. `max_tokens` is never lowered to or below the budget. Thinking blocks come back only when it is on. | | `output_config.effort` and `output_config.format` | Applied: a reasoning level, and a `json_schema` that the answer must follow. Other keys are accepted and not sent. | | `cache_control` on a block, and at the top level | Applied. See [Prompt caching](https://inference.ai.exchange/docs/caching.md). | | `image` blocks | Applied to offers that declare image input. The source can be `base64` or a `url`. See [Modalities](https://inference.ai.exchange/docs/modalities.md). | | `document` blocks | Applied to offers that declare file input. The source must be `base64`, because the exchange measures the file before it sets the cap. | | Any other content block in a user turn | `400 unsupported_content`. The message names the block. | | `POST /v1/messages/count_tokens` | An estimate from the exchange, not a provider tokenizer. It counts the text of `system` and `messages`, not tools, images or documents. | | Message Batches API, Files API | Not available. Send each request alone, and send a document as `base64`. | ### Troubleshooting For `402 insufficient_balance` and `400 no_eligible_offer`, see [What is different about money](https://inference.ai.exchange/docs/move-from-openrouter.md#what-is-different-about-money). `error.type` follows the HTTP status. Match on `code`. | Error | Cause | Fix | | ----------------------------------------------------------------- | ------------------------------------------------------------------ | ---------------------------------------------------------------------------- | | `404` for `/v1/v1/messages` | The base URL ends in `/v1`. | Remove `/v1`. | | `401 authentication_error` | The key is wrong, revoked or expired. | Send a current key in `x-api-key`. See [API keys](https://inference.ai.exchange/docs/keys.md). | | `404 not_found_error`, `code` is `model_not_found` | The `model` is not on the exchange. | Pick a name from `GET /v1/anthropic/models`. | | `400`, `code` is `unsupported_parameter`, `param` is `tools[...]` | The request has a hosted tool. | Remove the tool. | | `400`, `code` is `unsupported_content` | A block type is unknown, or a `document` has a `url` source. | Send the document as `base64`, or remove the block. | | `stop_reason` is `max_tokens` and the answer has no text | A model that thinks by default used the output limit for thinking. | Send a larger `max_tokens`. | | `503 overloaded_error` | The awarded provider failed, or no seller can serve the model now. | Try again later, or select another model. See [Errors](https://inference.ai.exchange/docs/errors.md#auction). |