Developers

Lucius developers

Agents and engineers can discover the Lucius API without a sales form. Create a key in the dashboard, or connect MCP over OAuth. This page is the index for OpenAPI, scopes, MCP, and the CLI.

Self-serve access

API keys. Sign in at app.lucius.finance, then Settings → API Keys → Create Key. Keys use the luc_live_ prefix and authenticate with Authorization: Bearer or X-Api-Key.

Sandbox. Development API: https://api-dev.lucius.finance. Same OpenAPI paths as production. Use a separate key per environment.

MCP. No key copy-paste. Add https://api.lucius.finance/mcp in Claude Code, Cursor, or Codex and complete the browser login. Request only the scopes you need.

CLI. npx @lucius-finance/cli --help — list contracts, submit usage, and print the OpenAPI URL.

Machine-readable files

  • OpenAPI specification

    Machine-readable Billing API at /openapi.json (YAML at /openapi.yaml). Every operation has an operationId, description, typed parameters, and response schemas.

  • Lucius MCP server

    Streamable HTTP at https://api.lucius.finance/mcp. OAuth 2.1 PKCE — no API key to paste. Manifests at /.well-known/mcp.json and /.well-known/mcp/server-card.json.

  • Billing API docs

    Human docs for usage events, contracts, and invoices. Quickstart, authentication, pagination, and errors.

  • Scoped permissions

    RFC 9728 protected-resource metadata with scopes_supported. Named OAuth scopes also appear in the OpenAPI security schemes.

OAuth scopes

Least-privilege scopes for MCP and agents. Declared in OpenAPI OAuth2 and in /.well-known/oauth-protected-resource.

  • read:analytics — burn, runway, forecasts
  • read:reports— P&L, balance sheet, cash flow
  • read:transactions — bank balances and transactions
  • read:invoices — AR, AP, customers, contracts
  • read:ledger — journal entries and COA
  • write:invoices / write:transactions / write:ledger / write:tax — mutations
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