Claude API and MCP: how to connect the language model to your project
Claude is a family of language models that understand and write text, work with code, answer questions and hold conversations. NeuralSpace offers four versions: the fast and affordable Claude Haiku 4.5, the balanced Claude Sonnet 5, the most powerful Claude Opus 5 and Claude Fable 5. All of them run through a single public API, and there is a ready MCP server for AI agents. The key is issued on the API keys page.
What the Claude models can do
The models take a text prompt and return an answer, support system instructions and a response length limit. Haiku 4.5 suits fast replies and high volume, Sonnet 5 suits everyday text and code work, Opus 5 suits complex reasoning and long tasks, and Fable 5 suits creative writing and dialogue. The same model is available both in the site chat and through the API.
API endpoint
Send a request to POST /v1/messages in the Anthropic format. A minimal example: {"model": "claude-sonnet-5", "max_tokens": 1024, "messages": [{"role": "user", "content": "Write a short greeting"}]}. The answer comes in the content field and token usage in usage. Authorization uses an API key in the x-api-key header.
MCP tools
The NeuralSpace MCP server is available at POST /mcp (Streamable HTTP). To work with Claude, an agent calls the chat tool with model and prompt parameters, plus list_models for the model and price list and get_balance to check funds. This lets Claude Code, Cursor and other MCP clients use the site models directly.
How to connect
Sign up on NeuralSpace, open the API keys page and create an nsk-… key. Then pass it in the request header or in your MCP client settings. Full documentation is on the /v1/docs page.
FAQ
Which Claude model is the fastest?
Claude Haiku 4.5 — it is cheaper and faster than the others and suits high-volume requests.
How does Opus 5 differ from Sonnet 5?
Opus 5 is more powerful and handles complex reasoning better, but costs more. Sonnet 5 is the price-quality balance.
Where do I get an API key?
In the dashboard on the API keys page — the key is created in one click.