See the API reference for full documentation on available parameters.
Basic request and response
{
"id": "msg_01XFDUDYJgAACzvnptvVoYEL",
"type": "message",
"role": "assistant",
"content": [
{
"type": "text",
"text": "Hello!"
}
],
"model": "claude-3-5-sonnet-20241022",
"stop_reason": "end_turn",
"stop_sequence": null,
"usage": {
"input_tokens": 12,
"output_tokens": 6
}
}
Multiple conversational turns
The Messages API is stateless, which means that you always send the full conversational history to the API. You can use this pattern to build up a conversation over time. Earlier conversational turns don’t necessarily need to actually originate from Claude — you can use synthetic assistant messages.
#!/bin/sh
curl https://api.anthropic.com/v1/messages \
--header "x-api-key: $ANTHROPIC_API_KEY" \
--header "anthropic-version: 2023-06-01" \
--header "content-type: application/json" \
--data \
'{
"model": "claude-3-5-sonnet-20241022",
"max_tokens": 1024,
"messages": [
{"role": "user", "content": "Hello, Claude"},
{"role": "assistant", "content": "Hello!"},
{"role": "user", "content": "Can you describe LLMs to me?"}
]
}'
import anthropic
message = anthropic.Anthropic().messages.create(
model="claude-3-5-sonnet-20241022",
max_tokens=1024,
messages=[
{"role": "user", "content": "Hello, Claude"},
{"role": "assistant", "content": "Hello!"},
{"role": "user", "content": "Can you describe LLMs to me?"}
],
)
print(message)
import Anthropic from '@anthropic-ai/sdk';
const anthropic = new Anthropic();
await anthropic.messages.create({
model: 'claude-3-5-sonnet-20241022',
max_tokens: 1024,
messages: [
{"role": "user", "content": "Hello, Claude"},
{"role": "assistant", "content": "Hello!"},
{"role": "user", "content": "Can you describe LLMs to me?"}
]
});
{
"id": "msg_018gCsTGsXkYJVqYPxTgDHBU",
"type": "message",
"role": "assistant",
"content": [
{
"type": "text",
"text": "Sure, I'd be happy to provide..."
}
],
"stop_reason": "end_turn",
"stop_sequence": null,
"usage": {
"input_tokens": 30,
"output_tokens": 309
}
}
Putting words in Claude’s mouth
You can pre-fill part of Claude’s response in the last position of the input messages list. This can be used to shape Claude’s response. The example below uses "max_tokens": 1 to get a single multiple choice answer from Claude.
{
"id": "msg_01Q8Faay6S7QPTvEUUQARt7h",
"type": "message",
"role": "assistant",
"content": [
{
"type": "text",
"text": "C"
}
],
"model": "claude-3-5-sonnet-20241022",
"stop_reason": "max_tokens",
"stop_sequence": null,
"usage": {
"input_tokens": 42,
"output_tokens": 1
}
}
Vision
Claude can read both text and images in requests. Currently, we support the base64 source type for images, and the image/jpeg, image/png, image/gif, and image/webp media types. See our vision guide for more details.
{
"id": "msg_01EcyWo6m4hyW8KHs2y2pei5",
"type": "message",
"role": "assistant",
"content": [
{
"type": "text",
"text": "This image shows an ant, specifically a close-up view of an ant. The ant is shown in detail, with its distinct head, antennae, and legs clearly visible. The image is focused on capturing the intricate details and features of the ant, likely taken with a macro lens to get an extreme close-up perspective."
}
],
"model": "claude-3-5-sonnet-20241022",
"stop_reason": "end_turn",
"stop_sequence": null,
"usage": {
"input_tokens": 1551,
"output_tokens": 71
}
}
See our guide for examples for how to use tools with the Messages API.
See our computer use (beta) guide for examples of how to control desktop computer environments with the Messages API.
