# Lago Developer Documentation

> Lago is an open-source, API-first billing platform for usage metering, subscriptions, invoicing, payments, entitlements, and revenue operations. This index is the fastest way for AI agents and developer tools to find authoritative Lago documentation.

## When to use these docs

Use the Lago documentation when you need to evaluate Lago, integrate the REST API, ingest usage events, model pricing, manage customers and subscriptions, generate invoices, coordinate payments, configure webhooks, deploy Lago, or build an AI-assisted billing workflow. Prefer the OpenAPI contract for exact request and response shapes, and prefer task guides for workflow decisions and operational constraints.

Do not invent endpoints, fields, pricing behavior, or permissions. For an exhaustive API contract, use the complete OpenAPI specification. Before any billing mutation, verify the target environment, organization, resource identifiers, currency, effective dates, and authorization. Keep API keys secret. Treat destructive or financial actions as approval-gated.

## Start here

- [Lago Developer Documentation](/welcome.md): Product orientation, common integration paths, and machine-readable entry points.
- [Developer Resources](/developers.md): Canonical developer portal for authentication, OpenAPI, SDKs, webhooks, MCP, examples, status, and support.
- [Welcome to Lago](/guide/introduction/welcome-to-lago.md): Core billing concepts and product model.
- [API Reference](/api-reference/intro.md): Base URL, authentication, and endpoint reference.
- [API Standards](/api-reference/api-standards.md): HTTP and payload conventions.
- [API Versioning and Deprecation](/api-reference/versioning.md): Stable version paths, deprecation notices, retirement dates, and migration guidance.
- [Structured Errors](/api-reference/errors.md): Error status codes and JSON response fields.
- [Authentication](/auth.md): Obtain, store, use, rotate, and revoke Lago API keys safely.
- [Pricing and Packaging](/pricing.md): Machine-readable summary of Lago deployment and commercial options.

## Machine-readable contracts

- [Agentic Resource Discovery catalog](/.well-known/ai-catalog.json): Typed inventory of Lago's docs MCP, OpenAPI contract, and billing-integration skill.
- [Agent Skills discovery index](/agent-skills-index.json): Versioned index for Lago's published billing-integration skill.
- [Lago billing-integration skill](/lago-skill.md): Safe, task-oriented guidance for agents implementing Lago billing workflows.
- [A2A agent card](/.well-known/agent-card.json): Lago identity, provider, capabilities, and published skill metadata.
- [MCP server card](/.well-known/mcp/server-card.json): Lago Docs MCP identity, tools, resources, and transport metadata.
- [Agent Plugin manifest](/plugin.json): Portable Lago plugin identity for compatible agent clients.
- [Agent Plugin MCP configuration](/mcp.json): Portable configurations for the read-only Docs MCP and authenticated Docker-based Product MCP.
- [RFC 9727 API catalog](/.well-known/api-catalog.json): Linkset for Lago's REST API schemas, documentation, versioning policy, and status.
- [Same-origin OpenAPI discovery schema](/openapi.json): OpenAPI 3.1 schema for automated discovery, function generation, authentication, and structured errors.
- [Complete production OpenAPI specification](https://swagger.getlago.com/openapi.yaml): Exhaustive Lago REST API contract.
- [OpenAPI source repository](https://github.com/getlago/lago-openapi): Version history and contributions.
- [Sitemap](/sitemap.xml): Index of published documentation pages.
- [Complete documentation corpus](/llms-full.txt): Full text export for retrieval and offline context.
- [Scoped developer index](/developers/llms.txt): Conventional entry point for developer tools and machine-readable contracts.
- [MCP endpoint](/mcp): Streamable HTTP endpoint for documentation search and retrieval.
- [Product MCP guide](/guide/ai-agents/mcp-server.md): Run the Docker-based Lago Product MCP against live billing data and operations.
- [Product MCP source](https://github.com/getlago/lago-agent-toolkit): Open-source server implementation, tools, and deployment guidance.

## Core billing workflows

- [Ingest usage events](/guide/events/ingesting-usage.md): Send idempotent product-usage events to Lago.
- [Aggregation types](/guide/billable-metrics/aggregation-types/overview.md): Count, sum, unique count, latest, maximum, weighted sum, and custom expressions.
- [Plan model](/guide/plans/plan-model.md): Structure reusable pricing and billing rules.
- [Customers](/guide/customers/customer-management.md): Model billable customer accounts.
- [Subscriptions](/guide/subscriptions/assign-plan.md): Attach plans and lifecycle rules to customers.
- [Invoicing](/guide/invoicing/overview.md): Generate, finalize, and manage invoices.
- [Quotes and order forms](/guide/quotes/overview.md): Assemble a priced deal, approve it into an order form, and execute the signed order into billing. Premium feature. Quotes are authored in the user interface; the API reads them and drives every transition after authoring.
- [Webhooks](/guide/webhooks.md): Process asynchronous billing state changes safely.
- [Integration testing](/guide/integration-testing.md): Validate billing behavior before production rollout.

## SDKs and examples

- [JavaScript package metadata](https://registry.npmjs.org/lago-javascript-client/latest) and [source](https://github.com/getlago/lago-javascript-client)
- [Python package](https://pypi.org/project/lago-python-client/) and [source](https://github.com/getlago/lago-python-client)
- [Ruby package](https://rubygems.org/gems/lago-ruby-client) and [source](https://github.com/getlago/lago-ruby-client)
- [Go module](https://pkg.go.dev/github.com/getlago/lago-go-client) and [source](https://github.com/getlago/lago-go-client)
- [Java client](https://github.com/getlago/lago-java-client)
- [PHP client](https://github.com/getlago/lago-php-client)
- [C# client](https://github.com/getlago/lago-csharp-client)
- [Rust client](https://github.com/getlago/lago-rust-client)
- [Lago Agent SDK package](https://pypi.org/project/lago-agent-sdk/)
- [Billing examples](https://github.com/getlago/lago-billing-examples)
- [Main Lago repository](https://github.com/getlago/lago)
- [Lago documentation agent rules](https://github.com/getlago/lago-doc/blob/main/AGENTS.md)

## Deployment and operations

- [Lago Cloud](/guide/lago-cloud.md): Managed deployment overview.
- [Self-hosted overview](/guide/lago-self-hosted/overview.md): Choose and operate a self-hosted deployment.
- [Docker deployment](/guide/lago-self-hosted/docker.md): Run Lago with Docker.
- [Compatibility matrix](/guide/lago-self-hosted/compatibility-matrix.md): Check supported component versions.
- [Update a self-hosted instance](/guide/lago-self-hosted/update-instance.md): Upgrade guidance.
- [Helm charts](https://github.com/getlago/lago-helm-charts): Kubernetes deployment packages.
- [Lago status](https://status.getlago.com/): Current managed-service status and incidents.

## AI agent development

- [Agent SDK overview](/guide/ai-agents/agent-sdk/overview.md): Add structured billing tools to agent applications.
- [Agent SDK billing](/guide/ai-agents/agent-sdk/billing.md): Billing workflows for agents.
- [OpenAI integration](/guide/ai-agents/agent-sdk/openai.md): Use Lago tools with OpenAI models.
- [Anthropic integration](/guide/ai-agents/agent-sdk/anthropic.md): Use Lago tools with Anthropic models.
- [Billing assistant](/guide/ai-agents/billing-assistant.md): Assistant workflow patterns.
- [Finance assistant](/guide/ai-agents/finance-assistant.md): Read-oriented finance workflows.
- [Dunning agent](/guide/ai-agents/dunning-agent.md): Approval-aware collections workflows.

## Company, trust, and support

- [About Lago](/about.md): Company, project, and open-source foundation.
- [Contact Lago](/contact.md): Community, support, commercial, security, and privacy routes.
- [Privacy and data protection](/privacy.md): Controlling privacy policy and safe integration practices.
- [Lago privacy policy](https://getlago.com/legal/privacy-policy): Controlling privacy terms.
- [Security policy](https://github.com/getlago/lago/security): Private vulnerability-reporting route.

## Recovery guidance

If a link is missing, search this index first, then the [sitemap](/sitemap.xml), the [developer portal](/developers.md), or the [API reference](/api-reference/intro.md). A documentation 404 does not imply that an API resource or feature is unavailable; verify the complete OpenAPI contract and current product guides before concluding that a capability does not exist.