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Fermat

Official registry AI and agents

OpenAI-compatible LLM gateway: pay per request with an API key, signed receipt for each call.

Website

Install

Add this to your client's MCP configuration (Claude Desktop: claude_desktop_config.json; Cursor: .cursor/mcp.json; VS Code and others use the same "mcpServers" shape).

Remote (streamable-http)
Claude Code 
claude mcp add --transport http fermat 'https://mcp.fermat.ai.phase.xyz/mcp' --header 'Authorization: <Phase API key as '\''Bearer phk_...'\''>' --header 'X-Phase-BYOK-Anthropic: <Optional: your Anthropic API key, for Claude models>' --header 'X-Phase-BYOK-OpenAI: <Optional: your OpenAI API key, for GPT models>'
JSON configuration (Claude Desktop, Cursor, VS Code) 
{
    "mcpServers": {
        "fermat": {
            "type": "http",
            "url": "https://mcp.fermat.ai.phase.xyz/mcp",
            "headers": {
                "Authorization": "<Phase API key as 'Bearer phk_...'>",
                "X-Phase-BYOK-Anthropic": "<Optional: your Anthropic API key, for Claude models>",
                "X-Phase-BYOK-OpenAI": "<Optional: your OpenAI API key, for GPT models>"
            }
        }
    }
}

Frequently asked questions

What is Fermat?

OpenAI-compatible LLM gateway: pay per request with an API key, signed receipt for each call.

How do I install Fermat?

It runs as a remote server. In Claude Code: claude mcp add --transport http fermat 'https://mcp.fermat.ai.phase.xyz/mcp' --header 'Authorization: <Phase API key as '\''Bearer phk_...'\''>' --header 'X-Phase-BYOK-Anthropic: <Optional: your Anthropic API key, for Claude models>' --header 'X-Phase-BYOK-OpenAI: <Optional: your OpenAI API key, for GPT models>'. For other clients, paste the JSON configuration from this page into their MCP settings.

Does Fermat need an API key?

Yes. It expects Authorization, X-Phase-BYOK-Anthropic, X-Phase-BYOK-OpenAI, which you set in its configuration.

Who maintains Fermat?

It is published by xyz.phase.ai. AI.tn lists it but does not maintain or endorse it.

From the official MCP Registry. Listing is not an endorsement: review a server's code and permissions before giving it access to your data.