API Inventory
Pronunciation: A-P-I IN-vun-tor-ee
Definition
An API inventory is a maintained register of all APIs, endpoints, credentials, owners, versions and data flows used by an organization.
Overview
What it means
An API inventory is a maintained register of all APIs, endpoints, credentials, owners, versions and data flows used by an organization. For payment businesses it is essential for security and reliable integration changes.
How it works
A practical inventory identifies production and test endpoints, authentication methods, permissions, webhook URLs, vendor dependencies, rate limits, connected applications, log locations and retirement dates. Discovery can use gateway logs, source repositories, deployment configuration and provider dashboards, then owners confirm the records.
Understanding the technical details
The inventory should be actionable during an incident: who owns the integration, where the secret lives, which production funds it can affect and how to revoke it. A table without accountable owners becomes stale quickly. Include webhook URLs, third-party SDK versions and sandbox endpoints, which are often overlooked. Tie changes to deployment review, and retire unused keys before deleting old documentation. Avoid copying secrets into the inventory; record secure vault references instead. A quarterly access review can compare listed integrations with real credential usage and revoke tokens that have not been used for a documented period. This makes the inventory a security control rather than just a spreadsheet.
Common failures and limitations
An inventory quickly becomes stale if not updated through deployment and change-management procedures. Forgotten API keys and abandoned callback endpoints expand the attack surface. Avoid publishing secrets in the inventory itself; store secure references instead.
Related concepts
Webhook, Webhook Verification, Merchant API Key.
Further reading
Example
A company migrates its crypto gateway and finds three old webhook endpoints that still accept requests. The API inventory reveals their owners and permits controlled decommissioning without silently breaking invoice notifications.
Comparison
An API inventory catalogs integration surfaces and responsibilities. API documentation teaches callers how an endpoint works, while an API gateway mediates traffic and enforcement at runtime.
Key Takeaway
An inventory quickly becomes stale if not updated through deployment and change-management procedures.
Sources
- OWASP API Security Top 10 – 2023 — OWASP (2026-08-03)
- Secure Software Development Framework, SP 800-218 — NIST (2026-08-03)
- Security and Privacy Controls for Information Systems and Organizations, SP 800-53 Rev. 5 — NIST (2026-08-03)