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 and Claude Code.

Change these three things

Issue a spend key on the API keys page. See API keys.
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.
Change each model to a name that GET /v1/anthropic/models lists. See Model names.

Then check these:

Keep max_tokens in each request. The exchange requires it.
Remove each server tool. See Anthropic features.
Run a dry run.
Read 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.

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"},
)

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.

Model names

Send a name that GET /v1/anthropic/models returns, a router model, a basket or a preset. See Connect an app. 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.

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.
`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.
`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.
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.
`image` blocks	Applied to offers that declare image input. The source can be `base64` or a `url`. See Modalities.
`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. 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.
`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.