Anthropic offers two ways to build with Claude, each suited to different use cases:
| Messages API | Claude Managed Agents | |
|---|---|---|
| What it is | Direct model prompting access | Pre-built, configurable agent harness that runs in managed infrastructure |
| Best for | Custom agent loops and fine-grained control | Long-running tasks and asynchronous work |
| Learn more | Messages API docs | Claude Managed Agents docs |
本指南涵盖了使用 Messages API 的常见模式,包括基本请求、多轮对话、预填充技术和视觉功能。有关完整的 API 规范,请参阅 Messages API 参考。
This feature is eligible for Zero Data Retention (ZDR). When your organization has a ZDR arrangement, data sent through this feature is not stored after the API response is returned.
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#!/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-opus-4-6",
"max_tokens": 1024,
"messages": [
{"role": "user", "content": "Hello, Claude"}
]
}'{
"id": "msg_01XFDUDYJgAACzvnptvVoYEL",
"type": "message",
"role": "assistant",
"content": [
{
"type": "text",
"text": "Hello!"
}
],
"model": "claude-opus-4-6",
"stop_reason": "end_turn",
"stop_sequence": null,
"usage": {
"input_tokens": 12,
"output_tokens": 6
}
}Messages API 是无状态的,这意味着您始终需要将完整的对话历史发送给 API。您可以使用此模式随时间构建对话。早期的对话轮次不一定需要真正来自 Claude。您可以使用合成的 assistant 消息。
#!/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-opus-4-6",
"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
}
}您可以在输入消息列表的最后位置预填充 Claude 响应的一部分。这可以用来塑造 Claude 的响应。下面的示例使用 "max_tokens": 1 从 Claude 获取单个多项选择答案。
#!/bin/sh
curl https://api.anthropic.com/v1/messages \
--header "x-api-key: $ANTHROPIC_API_KEY" \
--header "anthropic-version: 2023-06-01" \
--header "content-type: application/json" \
--data \
'{
"model": "claude-sonnet-4-5",
"max_tokens": 1,
"messages": [
{"role": "user", "content": "What is latin for Ant? (A) Apoidea, (B) Rhopalocera, (C) Formicidae"},
{"role": "assistant", "content": "The answer is ("}
]
}'{
"id": "msg_01Q8Faay6S7QPTvEUUQARt7h",
"type": "message",
"role": "assistant",
"content": [
{
"type": "text",
"text": "C"
}
],
"model": "claude-sonnet-4-5",
"stop_reason": "max_tokens",
"stop_sequence": null,
"usage": {
"input_tokens": 42,
"output_tokens": 1
}
}预填充功能不支持 Claude Mythos Preview、Claude Opus 4.6 和 Claude Sonnet 4.6。对这些模型使用预填充的请求将返回 400 错误。请改用结构化输出或系统提示指令。有关迁移模式,请参阅迁移指南。
Claude 可以读取请求中的文本和图像。图像可以使用 base64、url 或 file 源类型提供。file 源类型引用通过 Files API 上传的图像。支持的媒体类型为 image/jpeg、image/png、image/gif 和 image/webp。详情请参阅视觉指南。
#!/bin/sh
# 选项 1:Base64 编码的图像
IMAGE_URL="https://upload.wikimedia.org/wikipedia/commons/a/a7/Camponotus_flavomarginatus_ant.jpg"
IMAGE_MEDIA_TYPE="image/jpeg"
IMAGE_BASE64=$(curl "$IMAGE_URL" | base64 | tr -d '\n')
curl https://api.anthropic.com/v1/messages \
--header "x-api-key: $ANTHROPIC_API_KEY" \
--header "anthropic-version: 2023-06-01" \
--header "content-type: application/json" \
--data \
'{
"model": "claude-opus-4-6",
"max_tokens": 1024,
"messages": [
{"role": "user", "content": [
{"type": "image", "source": {
"type": "base64",
"media_type": "'$IMAGE_MEDIA_TYPE'",
"data": "'$IMAGE_BASE64'"
}},
{"type": "text", "text": "What is in the above image?"}
]}
]
}'
# 选项 2:URL 引用的图像
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-opus-4-6",
"max_tokens": 1024,
"messages": [
{"role": "user", "content": [
{"type": "image", "source": {
"type": "url",
"url": "https://upload.wikimedia.org/wikipedia/commons/a/a7/Camponotus_flavomarginatus_ant.jpg"
}},
{"type": "text", "text": "What is in the above image?"}
]}
]
}'{
"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-opus-4-6",
"stop_reason": "end_turn",
"stop_sequence": null,
"usage": {
"input_tokens": 1551,
"output_tokens": 71
}
}