Why You Need an API Inventory & 8 Steps to Building One

What Is API Inventory?

API inventory refers to the comprehensive collection of APIs that an organization manages and uses for its various operations and services. This inventory should include all the APIs an organization has developed or integrated with, including internal, external, public, and private APIs. 

The purpose of maintaining such an inventory is to have a clear overview of the API assets available within the organization. This enables better management, security, and utilization of these resources. 

Beyond listing available APIs, the inventory process involves understanding their functionalities, operational status, and how they interact with different parts of the system. A central repository stores information about each API’s purpose, capabilities, limitations, and technical specifications. 

This is part of a series of articles about API security.

Why Is API Inventory Important? 

An API inventory allows organizations to protect their digital assets against emerging security threats. By maintaining an up-to-date inventory, organizations gain visibility into all APIs in operation, including those that might be obsolete or undocumented. This informs the API security strategy, allowing for the identification and mitigation of vulnerabilities. 

An extensive API inventory supports compliance with data protection regulations by ensuring that all APIs handling sensitive information are accounted for and adequately secured. 

Other advantages include improved resource allocation and operational efficiency. Having a centralized inventory prevents the duplication of efforts by providing teams with a clear understanding of existing APIs and their functionalities. It highlights underutilized or redundant APIs that can be optimized or decommissioned. 

Why Do Organizations Struggle to Build an API Inventory? 

With the continuous development and deployment of new APIs, alongside frequent updates to existing ones, keeping an inventory up-to-date becomes a significant challenge. This situation is compounded by the adoption of microservices architecture, which increases the number of APIs exponentially. 

Many organizations lack a centralized system for tracking APIs, resulting in scattered information across various teams and platforms. This decentralization makes it hard to maintain a comprehensive view of all APIs, leading to gaps in the inventory. Another major obstacle is the reliance on manual processes for cataloging APIs, which are time-consuming and error-prone. 

Some organizations may not fully recognize the importance of an API inventory until they encounter security breaches or compliance issues stemming from undocumented or unsecured APIs. This reactive approach hinders effective API management.

What Is API Inventory Management?

API inventory management involves overseeing and controlling an organization’s API assets throughout their lifecycle. This includes systematic tracking, documenting, and analyzing all APIs that an organization has developed or integrated with. It aims to ensure that APIs are efficiently utilized, securely maintained, and aligned with business objectives. 

By properly managing the API inventory, organizations can optimize their digital ecosystem’s performance and security posture. This requires establishing standards for API development and documentation, monitoring API usage to identify trends or anomalies, and enforcing security policies to protect against unauthorized access. 

Effective API inventory management also involves regularly reviewing and updating APIs to reflect changes in technology or business requirements. 

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How to to Catalog Your API Inventory

Here’s an outline of the steps involved in building an API inventory.

1. Identify APIs 

Start by identifying all APIs within the organization’s ecosystem. This includes distinguishing between internal, external, and third-party APIs. Internal APIs are those developed in-house to facilitate backend processes or inter-service communication. External APIs are integrated from outside sources to add functionalities like payment processing or social media integration. 

Third-party APIs refer to services provided by external entities that are utilized within the organization’s applications. By identifying these APIs, organizations can categorize them and understand what needs to be documented.

Tzvika Shneider

CEO, Pynt

Tzvika Shneider is a 20-year software Security industry leader with a robust background in product and software management.

Tips from the expert

• Use automated API discovery tools: Leverage automated tools to continuously scan your environment for undocumented APIs, reducing the risk of shadow APIs that can lead to security gaps.
• Set up access controls for API inventory: Restrict access to the API inventory to authorized personnel only, reducing the risk of unauthorized changes or exposure of sensitive information.
• Ensure integration with CI/CD pipelines: Embed API inventory management into CI/CD pipelines to automatically update the inventory with new or modified APIs as part of the deployment process.
• Establish a standardized documentation template: Use a consistent template for documenting API details to maintain uniformity and make it easier for teams to navigate the inventory.
• Provide API usage guidelines: Include usage guidelines and best practices in the inventory to help developers understand the appropriate use of each API, minimizing misuse and security risks.

2. Document API Details 

Document the attributes of each API, such as its purpose, the technology used (e.g., RESTful, SOAP), and its current status (active, deprecated). This step ensures that all relevant information about an API is captured systematically. The documentation should record each API’s name, description, version information, endpoint URLs, and any authentication methods required. 

The API’s name should be concise but descriptive enough to give an immediate understanding of its function. The description should further elaborate on the API’s capabilities, use cases, and any limitations or conditions of use. 

3. Categorize APIs 

Group the APIs according to their functionality, technology, or business domain. For example, APIs can be classified based on their use cases such as authentication, payment processing, or data retrieval. This organization enables developers and stakeholders to quickly access and understand the API’s purpose. 

Categorizing by technology—RESTful, SOAP, GraphQL—can also help in identifying the technical requirements and integration patterns needed for each API type. Tags can denote attributes like the API’s deployment environment (development, testing, production), its accessibility (public, private), or any relevant business unit it supports. 

4. Define API Metadata 

Specify details that describe and provide context for an API, including ownership information, usage policies, and technical specifications. Metadata guides developers and users by offering insights into the API’s functionality, limitations, and integration requirements. 

The metadata should include the API owner’s contact information, enabling users to reach out to them. It should also outline the data schema, response types, authentication requirements, and rate limits (if applicable). This ensures that users know how to interact with the API and what to expect in terms of performance and constraints.

5. Document API Dependencies

Map out how APIs are interconnected, including any third-party services they rely on or other internal APIs they interact with. By clearly identifying these dependencies, the organization can anticipate the impact of changes or updates to one API on others. Documenting dependencies also helps in risk assessment, anticipating when a critical API or service is unavailable.

6. Add Versioning Information 

Include information such as version numbers, release dates, and a summary of changes with each version. This helps developers understand the progression and modifications made to an API. It ensures backward compatibility, preventing updates from disrupting existing integrations. Documenting deprecated versions with reasons for their deprecation helps guide developers towards using the most current and supported versions.

7. Ensure Discoverability 

Implement a searchable catalog interface where users can easily find APIs based on functionality, technology, or business domain. Discoverability enhances the user experience and accelerates development processes. This can be achieved using filters, tags, and categorization, allowing developers to quickly locate the APIs that best suit their requirements. 

8. Keep the Catalog Up to Date 

Regularly update the API catalog to maintain its accuracy and relevance. This involves periodically reviewing the catalog to incorporate new APIs, retire obsolete ones, and reflect any changes to existing APIs, such as updates in versioning or modifications in functionality. Establish a routine for these updates to ensure the catalog remains a reliable resource. 

Learn more in our detailed guide to api security standards

Boost Your Security Posture With Automated API Discovery

Manual methods can no longer make the cut for companies in 2024.

Leveraging an automated approach to API discovery by using tools, scripts, or platforms, will automatically identify and document all your APIs.

With Pynt's API Security testing autopilot, you will be able to see your entire API inventory, and know where your APIs are - and where they aren't. See which endpoints are in production, and run a gap analysis between production and testing environments. Pynt easily syncs data from AWS, Azure and Kong API getaways and uncovers:

• New API in development: Devs are working on a new API - FYI!
• Shadow API:  Endpoints you might not know since we found them only in prod, and not in your tests or documentation.
• Undocumented API:  There’s an API in prod and testing, however not in API documentation.

Learn more in our detailed guide to shadow api