API Inventory

Overview

An API Inventory is an authoritative catalog of APIs, endpoints, versions, owners, environments, consumers, data classifications, dependencies, authentication methods, and operational status. The control exists to prevent APIs and applications from allowing unauthorized data access, privileged functions, unsafe state changes, or execution through defective design or implementation. It differs from API documentation because an inventory is a governance and exposure record, including undocumented, deprecated, internal, partner, and test interfaces. It should be interpreted alongside Asset Inventory because the concepts can affect the same decision without representing the same control, event, or risk.

The workflow starts with explicit trust boundaries, identities, objects, fields, functions, states, and allowed transitions. Server-side controls validate every request, use restrictive schemas, calculate authoritative values, and reject operations that violate authorization, sequence, rate, content, or business rules. In this context, discovery should combine repositories, gateways, traffic, cloud resources, specifications, DNS, and developer records, then reconcile duplicates and assign ownership, lifecycle status, and remediation deadlines.

It should connect the term to Attack Surface Management (ASM) where that relationship changes access, transaction treatment, investigation, communication, or recovery.

Testing should include positive and negative authorization cases, multiple roles and tenants, malformed and replayed requests, concurrency, version changes, nested data, recovery paths, and production-like configurations. Logs should connect principal, request, resource, decision, error, and resulting state without recording secrets.

Useful measures include endpoint coverage, failed authorization tests, vulnerable versions, time to remediate, abuse attempts, error and rejection rates, recurring defect classes, and differences between specification and deployed behavior.

The relationship with API Lifecycle should be documented where it affects residual risk or control ownership.