claude opus 4.5 Blogg

$There isn’t a model called “Claude Opus 4.5.” You likely mean Claude 3 Opus. Below is a quick guide to calling Anthropic’s Messages API with Claude 3 Opus. Quick start - Get an API key: create it in the Anthropic console. - Endpoint: POST https://api.anthropic.com/v1/messages - Required headers: - x-api-key: YOUR_API_KEY - anthropic-version: 2023-06-01 - content-type: application/json - Choose a model: - claude-3-opus-20240229 (or claude-3-opus-latest) - Basic request fields: - model: the model ID above - messages: array of { role: "user" | "assistant", content: "…" } or content blocks - max_tokens: upper bound for response tokens (e.g., 1024) - temperature/top_p: sampling controls (optional) - system: optional system prompt - stream: true for server-sent events (optional) cURL example - Non-streaming: curl https://api.anthropic.com/v1/messages \ -H "x-api-key: $ANTHROPIC_API_KEY" \ -H "anthropic-version: 2023-06-01" \ -H "content-type: application/json" \ -d '{ "model": "claude-3-opus-latest", "max_tokens": 1024, "messages": [ {"role":"user","content":"Explain transformers in 3 sentences."} ] }' - Streaming (SSE): curl https://api.anthropic.com/v1/messages \ -H "x-api-key: $ANTHROPIC_API_KEY" \ -H "anthropic-version: 2023-06-01" \ -H "content-type: application/json" \ -d '{ "model": "claude-3-opus-latest", "max_tokens": 1024, "stream": true, "messages": [ {"role":"user","content":"Stream a short poem about the ocean."} ] }' Python example import os import requests API_KEY = os.environ["ANTHROPIC_API_KEY"] url = "https://api.anthropic.com/v1/messages" headers = { "x-api-key": API_KEY, "anthropic-version": "2023-06-01", "content-type": "application/json", } data = { "model": "claude-3-opus-latest", "max_tokens": 1024, "messages": [ {"role": "user", "content": "Write a haiku about debugging."} ], "temperature": 0.7 } resp = requests.post(url, headers=headers, json=data, timeout=60) resp.raise_for_status() out = resp.json() # out["content"] is an array of blocks; extract text blocks text = "".join(block.get("text","") for block in out.get("content", []) if block.get("type") == "text") print(text) Node.js example import fetch from "node-fetch"; const API_KEY = process.env.ANTHROPIC_API_KEY; const resp = await fetch("https://api.anthropic.com/v1/messages", { method: "POST", headers: { "x-api-key": API_KEY, "anthropic-version": "2023-06-01", "content-type": "application/json", }, body: JSON.stringify({ model: "claude-3-opus-latest", max_tokens: 1024, messages: [{ role: "user", content: "Give me a list of 5 creative icebreaker questions." }], }), }); const json = await resp.json(); const text = (json.content || []) .filter(b => b.type === "text") .map(b => b.text) .join(""); console.log(text); Tool use (function calling) overview - Add a tools array describing callable functions: - tools: [{ name, description, input_schema }] - The model may respond with a tool_use block (name + input). - You run the tool in your code, then send another request including a new user message with a tool_result block that references the tool_use_id and contains the tool’s output. - Continue until the model returns a final text answer. Multimodal (images) overview - In a user message, content can be blocks like: - { "type": "text", "text": "Describe this image." } - { "type": "image", "source": { "type": "base64", "media_type": "image/png", "data": "..." } } Best practices - Use claude-3-opus-latest unless you need a pinned version. - Set reasonable max_tokens to control cost. - Prefer streaming for long outputs or interactive UIs. - Implement retries with exponential backoff on 429/5xx. - Keep conversation history concise; send only what the model needs. If you actually meant Claude 3.5 Sonnet (often the strongest general model as of mid‑2024), swap the model to claude-3-5-sonnet-latest and the rest stays the same.$

Mar 27, 2026

claude opus 4.5

There isn’t a model called “Claude Opus 4.5.” You likely mean Claude 3 Opus. Below is a quick guide to calling Anthropic’s Messages API with Claude 3 Opus. Quick start - Get an API key: create it in the Anthropic console. - Endpoint: POST https://api.anthropic.com/v1/messages - Required headers: - x-api-key: YOUR_API_KEY - anthropic-version: 2023-06-01 - content-type: application/json - Choose a model: - claude-3-opus-20240229 (or claude-3-opus-latest) - Basic request fields: - model: the model ID above - messages: array of { role: "user" | "assistant", content: "…" } or content blocks - max_tokens: upper bound for response tokens (e.g., 1024) - temperature/top_p: sampling controls (optional) - system: optional system prompt - stream: true for server-sent events (optional) cURL example - Non-streaming: curl https://api.anthropic.com/v1/messages \ -H "x-api-key: $ANTHROPIC_API_KEY" \ -H "anthropic-version: 2023-06-01" \ -H "content-type: application/json" \ -d '{ "model": "claude-3-opus-latest", "max_tokens": 1024, "messages": [ {"role":"user","content":"Explain transformers in 3 sentences."} ] }' - Streaming (SSE): curl https://api.anthropic.com/v1/messages \ -H "x-api-key: $ANTHROPIC_API_KEY" \ -H "anthropic-version: 2023-06-01" \ -H "content-type: application/json" \ -d '{ "model": "claude-3-opus-latest", "max_tokens": 1024, "stream": true, "messages": [ {"role":"user","content":"Stream a short poem about the ocean."} ] }' Python example import os import requests API_KEY = os.environ["ANTHROPIC_API_KEY"] url = "https://api.anthropic.com/v1/messages" headers = { "x-api-key": API_KEY, "anthropic-version": "2023-06-01", "content-type": "application/json", } data = { "model": "claude-3-opus-latest", "max_tokens": 1024, "messages": [ {"role": "user", "content": "Write a haiku about debugging."} ], "temperature": 0.7 } resp = requests.post(url, headers=headers, json=data, timeout=60) resp.raise_for_status() out = resp.json() # out["content"] is an array of blocks; extract text blocks text = "".join(block.get("text","") for block in out.get("content", []) if block.get("type") == "text") print(text) Node.js example import fetch from "node-fetch"; const API_KEY = process.env.ANTHROPIC_API_KEY; const resp = await fetch("https://api.anthropic.com/v1/messages", { method: "POST", headers: { "x-api-key": API_KEY, "anthropic-version": "2023-06-01", "content-type": "application/json", }, body: JSON.stringify({ model: "claude-3-opus-latest", max_tokens: 1024, messages: [{ role: "user", content: "Give me a list of 5 creative icebreaker questions." }], }), }); const json = await resp.json(); const text = (json.content || []) .filter(b => b.type === "text") .map(b => b.text) .join(""); console.log(text); Tool use (function calling) overview - Add a tools array describing callable functions: - tools: [{ name, description, input_schema }] - The model may respond with a tool_use block (name + input). - You run the tool in your code, then send another request including a new user message with a tool_result block that references the tool_use_id and contains the tool’s output. - Continue until the model returns a final text answer. Multimodal (images) overview - In a user message, content can be blocks like: - { "type": "text", "text": "Describe this image." } - { "type": "image", "source": { "type": "base64", "media_type": "image/png", "data": "..." } } Best practices - Use claude-3-opus-latest unless you need a pinned version. - Set reasonable max_tokens to control cost. - Prefer streaming for long outputs or interactive UIs. - Implement retries with exponential backoff on 429/5xx. - Keep conversation history concise; send only what the model needs. If you actually meant Claude 3.5 Sonnet (often the strongest general model as of mid‑2024), swap the model to claude-3-5-sonnet-latest and the rest stays the same.

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