Configuration

Nexus uses TOML format for all configuration. The configuration file defines your servers, authentication, rate limits, and other settings.

By default, Nexus looks for nexus.toml in the current directory:

# Uses ./nexus.toml
nexus

# Or specify a custom config file
nexus --config /path/to/config.toml

Configuration uses standard TOML syntax:

# LLM providers
[llm.providers.openai]
type = "openai"
api_key = "{{ env.OPENAI_API_KEY }}"

# MCP servers
[mcp.servers.github]
url = "https://api.github.com/mcp"

Use {{ env.VARIABLE_NAME }} to reference environment variables:

[llm.providers.openai]
api_key = "{{ env.OPENAI_API_KEY }}"

[mcp.servers.database]
cmd = ["psql-mcp"]
env = {
  PGHOST = "{{ env.DB_HOST }}",
  PGPASSWORD = "{{ env.DB_PASSWORD }}"
}

1. Server Configuration - HTTP server, authentication, security, and rate limiting
2. LLM Configuration - AI model providers and routing
3. MCP Configuration - Model Context Protocol servers and tools
4. Telemetry Configuration - OpenTelemetry metrics, traces, and logs

• Start with Server Settings for basic server configuration
• Set up LLM Providers for AI model access
• Add MCP Servers for tool integration
• Configure Telemetry for observability