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curl https://api.usetokenless.com/anthropic/v1/messages \
  -H "x-api-key: $TOKENLESS_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "tokenless-pro",
    "max_tokens": 1024,
    "messages": [
      {"role": "user", "content": "Explain model routing in one paragraph."}
    ],
    "stream": true
  }'

event: message_start
data: {"message":{"content":[],"id":"msg_req_1e6255bf_5d10049d4ab0_1","model":"deepseek-v4-flash","role":"assistant","stop_reason":null,"stop_sequence":null,"type":"message","usage":{"input_tokens":0,"output_tokens":0}},"type":"message_start"}

event: content_block_start
data: {"content_block":{"thinking":"","type":"thinking"},"index":0,"type":"content_block_start"}

event: content_block_delta
data: {"delta":{"thinking":"We","type":"thinking_delta"},"index":0,"type":"content_block_delta"}

: intermediate thinking deltas omitted

event: content_block_stop
data: {"index":0,"type":"content_block_stop"}

event: content_block_start
data: {"content_block":{"text":"","type":"text"},"index":1,"type":"content_block_start"}

event: content_block_delta
data: {"delta":{"text":"Model routing is the process of intelligently directing a user's request to the most suitable AI model…","type":"text_delta"},"index":1,"type":"content_block_delta"}

event: content_block_stop
data: {"index":1,"type":"content_block_stop"}

event: message_delta
data: {"delta":{"stop_reason":"end_turn","stop_sequence":null},"type":"message_delta","usage":{"input_tokens":11,"output_tokens":227}}

event: message_stop
data: {"type":"message_stop"}
POST/anthropic/v1/messages
For the full upstream contract, see the Claude Messages API reference. 
curl https://api.usetokenless.com/anthropic/v1/messages \
  -H "x-api-key: $TOKENLESS_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "tokenless-pro",
    "max_tokens": 1024,
    "messages": [
      {"role": "user", "content": "Explain model routing in one paragraph."}
    ],
    "stream": true
  }'

event: message_start
data: {"message":{"content":[],"id":"msg_req_1e6255bf_5d10049d4ab0_1","model":"deepseek-v4-flash","role":"assistant","stop_reason":null,"stop_sequence":null,"type":"message","usage":{"input_tokens":0,"output_tokens":0}},"type":"message_start"}

event: content_block_start
data: {"content_block":{"thinking":"","type":"thinking"},"index":0,"type":"content_block_start"}

event: content_block_delta
data: {"delta":{"thinking":"We","type":"thinking_delta"},"index":0,"type":"content_block_delta"}

: intermediate thinking deltas omitted

event: content_block_stop
data: {"index":0,"type":"content_block_stop"}

event: content_block_start
data: {"content_block":{"text":"","type":"text"},"index":1,"type":"content_block_start"}

event: content_block_delta
data: {"delta":{"text":"Model routing is the process of intelligently directing a user's request to the most suitable AI model…","type":"text_delta"},"index":1,"type":"content_block_delta"}

event: content_block_stop
data: {"index":1,"type":"content_block_stop"}

event: message_delta
data: {"delta":{"stop_reason":"end_turn","stop_sequence":null},"type":"message_delta","usage":{"input_tokens":11,"output_tokens":227}}

event: message_stop
data: {"type":"message_stop"}

Authorizations

​
x-api-key
string
header
required

Tokenless API key. Include anthropic-version on Anthropic-compatible requests.

Headers

​
anthropic-version
string
required

Selects the Anthropic-compatible response format.

Body

application/json
​
model
enum<string>
required
Available options:
tokenless-pro,
tokenless-max,
tokenless-ultra-saver
​
max_tokens
integer
required
Required range: x >= 1
​
messages
object[]
required
Minimum array length: 1
​
stream
boolean
default:false

Response

An Anthropic-compatible message response or SSE stream.