How much does the Claude Sonnet 5 API cost?

On FastMetal, Claude Sonnet 5 is billed per token in yen: ¥357.4 per 1M input tokens and ¥1,787 per 1M output tokens, before tax. Usage is drawn from a prepaid balance; there is no subscription or monthly fee.

Can I call Claude Sonnet 5 with the OpenAI SDK?

Yes. Point base_url at https://api.fastmetal.ai/v1 and pass "anthropic-claude-sonnet-5" as the model; existing OpenAI-style code works unchanged, including streaming, tool calls and structured output.

What is the context window of Claude Sonnet 5?

1,000,000 tokens, shared between the prompt and the response.

How does Claude Sonnet 5 rank?

#32 on the public arena's Japanese board (ELO 1,447). Ranks move as the leaderboard is updated.

What do I need to try Claude Sonnet 5?

Create an account and add credit; the model is then available both in the browser chat and over the API. There is no contract or minimum spend.

Back to Models

anthropic/claude-sonnet-5

Claude Sonnet 5

Sonnet 5 is Anthropic's most capable Sonnet-class model, with frontier performance across coding, agents, and professional work. It supports adaptive thinking with selectable reasoning effort levels (low, medium, high, max,...

6/30/2026

1,000,000 tokens

#22 Text (german)

Input: ¥357.4/M

Output: ¥1,787/M

Try in Chat Get API Key

Specifications

Modalities

Input

text

image

file

Output

text

Supported Parameters

include_reasoning

max_completion_tokens

max_tokens

reasoning

reasoning_effort

response_format

stop

structured_outputs

tool_choice

tools

verbosity

Max Output Tokens

128,000

Reasoning Configuration

Default: Thinking on (effort: high)
Selectable effort levels: max
xhigh
high
medium
low
Turning thinking off: Possible (reasoning.enabled: false)

How to control thinking, and what it costs

Code Examples

curl https://api.fastmetal.ai/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "anthropic-claude-sonnet-5",
    "messages": [{"role": "user", "content": "Hello!"}]
  }'

How Claude Sonnet 5 actually answers

Real responses to our standard prompts, recorded on FastMetal.

Count the number of 'r's in 'strawberry'

Count the number of 'r's in 'strawberry'. Explain your reasoning step by step.

# Counting 'r's in "strawberry" **Step 1: Spell out the word letter by letter** s - t - r - a - w - b - e - r - r - y **Step 2: Number each letter position** | Position | Letter | |----------|--------| | 1 | s | | 2 | t | | 3 | **r** | | 4 | a | | 5 | w | | 6 | b | | 7 | e | | 8 | **r** | | 9 | **r** | | 10 | y | **Step 3: Identify and count the 'r's** - Position 3: **r** ✓ (1st r) - Position 8: **r** ✓ (2nd r) - Position 9: **r** ✓ (3rd r) **Answer: There are 3 r's in "strawberry"**

5.9s response405 output tokens

Debug This Error

I'm getting the following error in my Node.js application: TypeError: Cannot read properties of undefined (reading 'map') at UserList (/app/components/UserList.js:12:25) at renderWithHooks (/app/node_modules/rea…

# Root Cause The `UserList` component receives `users` as a prop, but at the time it's rendered, `users` is `undefined` — not an empty array, but literally missing. When your code tries to call `.map()` on `undefined`, JavaScript throws that `TypeError`. This typically happens when: - The parent component hasn't fetched the data yet (e.g., an API call is still in progress) - The prop name doesn't match what's being passed down (typo) - The data source (API/state) genuinely returns `undefined` in some case # Fixes **1. Add a default prop value (quick fix)** ```jsx function UserList({ users = [] }) { return ( <ul> {users.map(user => <li key={user.id}>{user.name}</li>)} </u…

8.8s response750 output tokens

Code Review

Please review the following Python function and suggest improvements for readability, performance, and best practices: def get_data(url, retries=3): import requests import time for i in range(retries):…

## Review of `get_data` Function Here's an improved version followed by an explanation of the changes: ```python import logging import time from typing import Any import requests logger = logging.getLogger(__name__) def get_data( url: str, retries: int = 3, timeout: float = 10.0, backoff_factor: float = 2.0, ) -> list[dict[str, Any]]: """ Fetch active items from the given URL. Args: url: The endpoint to fetch data from. retries: Number of attempts before giving up. timeout: Request timeout in seconds. backoff_factor: Multiplier for exponential backoff between retries. Returns: A list of dicts with "name" and "id"…

14.0s response1299 output tokens

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Frequently asked questions

How much does the Claude Sonnet 5 API cost?: On FastMetal, Claude Sonnet 5 is billed per token in yen: ¥357.4 per 1M input tokens and ¥1,787 per 1M output tokens, before tax. Usage is drawn from a prepaid balance; there is no subscription or monthly fee.
Can I call Claude Sonnet 5 with the OpenAI SDK?: Yes. Point base_url at https://api.fastmetal.ai/v1 and pass "anthropic-claude-sonnet-5" as the model; existing OpenAI-style code works unchanged, including streaming, tool calls and structured output.
What is the context window of Claude Sonnet 5?: 1,000,000 tokens, shared between the prompt and the response.
How does Claude Sonnet 5 rank?: #32 on the public arena's Japanese board (ELO 1,447). Ranks move as the leaderboard is updated.
What do I need to try Claude Sonnet 5?: Create an account and add credit; the model is then available both in the browser chat and over the API. There is no contract or minimum spend.