Create a message

Anthropic-compatible Messages endpoint. Accepts the Anthropic Messages request shape and routes to any catalogued model.

Also served at /v1/anthropic/v1/messages; both paths accept the same requests. This bare path is what the Anthropic SDK builds from a bare-host base URL, so pointing the SDK at https://api-gateway.merge.dev works with no other changes.

Authentication

AuthorizationBearer

Your production key sent as a bearer token.

Request

This endpoint expects an object.

modelstringRequired

max_tokensintegerRequired

messageslist of objectsRequired

systemstring or list of objects or nullOptional

streambooleanOptionalDefaults to false

temperaturedouble or nullOptional

top_pdouble or nullOptional

top_kinteger or nullOptional

stop_sequenceslist of strings or nullOptional

toolslist of objects or nullOptional

tool_choicemap from strings to any or nullOptional

metadatamap from strings to any or nullOptional

service_tierstring or nullOptional

Response

Successful Response

idstring

type"message"

role"assistant"

modelstring

contentlist of objects

usageobject

stop_reasonenum or nullOptional

stop_sequencestring or nullOptional

Errors

422

Unprocessable Entity Error

$	curl -X POST https://api-gateway.merge.dev/v1/messages \
>	-H "Authorization: Bearer <token>" \
>	-H "Content-Type: application/json" \
>	-d '{
>	"model": "anthropic/claude-sonnet-5",
>	"max_tokens": 1024,
>	"messages": [
>	{
>	"role": "user",
>	"content": "What is the capital of France?"
>	}
>	]
>	}'

1	{
2	"id": "msg_a1b2c3d4e5f6",
3	"type": "message",
4	"role": "assistant",
5	"model": "anthropic/claude-sonnet-5",
6	"content": [
7	{
8	"type": "text",
9	"text": "The capital of France is Paris."
10	}
11	],
12	"usage": {
13	"input_tokens": 14,
14	"output_tokens": 8
15	},
16	"stop_reason": "end_turn",
17	"stop_sequence": null
18	}