What is API Discovery? How it Works, Use Cases & Tools

Key Takeaways

• Automated API discovery scans codebases, traffic, and systems to uncover all APIs, including shadow, undocumented, and zombie endpoints, helping prevent blind spots and reduce security risks.
• Continuous monitoring and inventory updates ensure newly added APIs are detected and obsolete ones are retired, maintaining accurate visibility across dynamic environments.
• Integrating API discovery into CI/CD pipelines enables real-time detection and security testing of APIs, reducing manual effort and eliminating gaps between development and production.
• Detecting and cataloging internal and external APIs improves governance, supports compliance, and ensures third-party services are securely integrated and monitored.
• Pynt automates discovery and security testing, highlights undocumented or shadow APIs, and integrates with CI/CD, cloud, and SIEM tools to streamline security workflows and reduce operational risk.

What is API Discovery? 

API discovery is a process that involves finding and understanding APIs (Application Programming Interfaces) that exist in a system or across multiple systems. APIs are an important building block in software applications. They define methods and data formats that a program should use to communicate with other software or with the operating system.‍‍

Some organizations take a manual approach to API discovery, where a developer or a team of developers goes through every piece of an application’s code to identify and document the APIs. However, many are turning to automated tools that can scan and detect APIs across various systems in a faster, more efficient manner.

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

Why Is API Discovery Important?

API discovery provides the foundation for secure, efficient, and scalable application ecosystems. Here are the key reasons it matters:

• Improved Application Development: Gives developers a clear view of existing APIs, reducing redundant work and enabling faster integrations. Understanding available APIs accelerates deployment and simplifies maintenance.
  
• Shadow and Zombie API Discovery: Identifies undocumented or unauthorized hidden APIs, including outdated zombie APIs, which can create security risks and compliance gaps if left unaddressed.
  
• Access to External Resources and Services: Maps out dependencies on third-party services, cloud platforms, and external APIs, improving reliability and supporting better API management practices.
  
• Compatibility with Existing Systems: Ensures that new software and upgrades align with current APIs, maintaining interoperability and minimizing disruptions across systems.

How API Discovery Works

API discovery identifies and inventories APIs by scanning systems, networks, and codebases. It can be carried out manually, automatically, or through a hybrid of both. The process involves analyzing traffic, inspecting code, and correlating findings to build a comprehensive API catalog.

Steps in the API Discovery Process

Here’s how a typical API discovery process unfolds:

1. Scan Network Traffic, Tests Traffic, and Logs

Tools either monitor live traffic or listen to traffic tests, to detect API calls, endpoints, and usage patterns - a critical first step to uncover hidden and undocumented APIs.

2. Inspect the Source Code and Documentation

Teams analyze code repositories to identify defined API endpoints.

3. Correlate Findings into an Inventory

Results from network and code analysis are consolidated to create a full inventory of both documented and hidden APIs, including shadow and zombie APIs.

4. Ongoing Monitoring and Updates

Continuous API discovery ensures the inventory stays up to date as new APIs are added or old ones are retired. Automated API discovery tools excel at maintaining this visibility over time.

The Risks Posed by Insecure APIs

Insecure or undocumented APIs weaken an organization’s security posture, exposing data, disrupting operations, and eroding customer trust. Recognizing these risks helps teams prioritize mitigation and maintain a secure API ecosystem.

Data Losses

APIs frequently handle sensitive business and personal data, including customer records, payment details, and proprietary information. When APIs lack proper encryption, access control, or validation, attackers can intercept requests, manipulate responses, or exploit misconfigurations to exfiltrate data. These breaches not only violate privacy regulations but also damage customer relationships and open organizations to hefty fines.

Service Disruption

APIs serve as the core of modern applications, but they can also become targets for denial-of-service (DoS) or resource exhaustion attacks. Exploiting weak rate limits or flooding endpoints with malformed requests can bring critical services offline or significantly degrade performance. Service disruptions harm productivity, impact customer experience, and can lead to missed business opportunities.

Loss of Reputation

Breaches and outages stemming from insecure APIs often attract public scrutiny. Media coverage, regulatory investigations, and negative customer sentiment can quickly erode an organization’s credibility. Even if the technical issues are resolved, rebuilding trust and recovering lost business can take years, making reputation loss one of the most damaging consequences of poor API security.

Broken Authentication

APIs that fail to enforce strong authentication and session controls allow unauthorized actors to impersonate legitimate users. Weak token validation, hardcoded credentials, and missing authorization checks can all lead to account takeovers or privilege escalation. This exposes sensitive data and puts the entire system at risk of complete compromise.

Injection Attacks

APIs that accept unvalidated input from clients are vulnerable to injection attacks, including SQL, NoSQL, command, or script injections. Attackers can craft malicious payloads that execute unintended commands on backend systems, exfiltrate data, or disrupt normal application logic. Such flaws are among the most common and severe security issues identified in API security testing.

Here follows a consolidated view of these risks, highlighting their nature, potential impact, and real-world examples to illustrate the consequences of insecure APIs.

Benefits of API Discovery

A comprehensive API discovery process delivers measurable benefits for both security and operational efficiency. Below are the key advantages of implementing API discovery effectively:

• Enhanced Security Posture: Identifies undocumented, hidden, and vulnerable APIs that attackers could exploit, helping teams close gaps and enforce security policies.
• Improved Developer Productivity: Provides developers with a clear inventory of existing APIs, enabling reuse, minimizing redundant work, and speeding up development cycles.
• Simplified Governance and Compliance: Ensures that all APIs are accounted for, properly documented, and aligned with internal governance policies and external regulatory requirements.
• Better API Lifecycle Management: Helps track APIs from development through deprecation, ensuring that outdated or unused APIs are retired and that active APIs remain secure and efficient.
• Increased Visibility into Hidden and Shadow APIs: Uncovers APIs that were deployed outside of official processes or forgotten over time, bringing them under proper management and reducing attack surfaces.
• Reduced Operational Risk through Proactive Monitoring: Enables continuous monitoring and assessment of APIs, allowing teams to address potential issues before they escalate into outages or breaches.

Types of API Discovery

Organizations approach API discovery in various ways, depending on their goals, resources, and environments. Below are the three most common distinctions to consider when designing a discovery strategy.

Manual vs. Automated Discovery

Manual discovery relies on developers or security teams inspecting code, documentation, and configurations to identify APIs. While it can provide a detailed understanding of system architecture, it is time-consuming, error-prone, and impractical at scale. Automated discovery uses specialized tools to scan networks, analyze traffic, and crawl systems, enabling the efficient and continuous detection of APIs. Automation improves accuracy and uncovers hidden or undocumented APIs with far less manual effort.

Passive vs. Active API Discovery

Passive discovery observes network traffic and logs to infer API usage without sending any requests. This non-intrusive approach works well in production environments but may miss dormant or rarely used endpoints. Active discovery, on the other hand, proactively probes systems, often with fuzzing or targeted scans, to uncover a broader set of APIs. While more thorough, active techniques require care to avoid unintended service disruption.

Internal vs. External API Discovery

Internal discovery focuses on APIs developed and hosted within the organization, ensuring private services are documented and secured. This helps maintain governance over microservices and internal integrations. External discovery targets third-party or public-facing APIs that the organization depends on. Documenting these external connections strengthens oversight of dependencies and ensures they meet security and compliance requirements.

API Discovery Use Cases

API discovery plays a critical role across a range of modern technology initiatives. Below are key use cases where API discovery provides measurable value:

• Enterprises Managing Microservices: In complex microservices architectures, API discovery helps map internal service interactions, identify redundant or outdated endpoints, and maintain governance over a fast-changing ecosystem.
  
• DevSecOps Automation Pipelines: API discovery integrates into DevSecOps workflows, ensuring new and existing APIs are detected, tested, and secured automatically as part of continuous integration and deployment processes.
  
• Regulatory Compliance and Audit Trails: Many data protection and privacy regulations require organizations to maintain an inventory of systems processing sensitive data. API discovery provides the visibility necessary to meet these compliance obligations and demonstrate due diligence during audits.
  
• Cloud Migration and Hybrid Environments: During migration to the cloud or adoption of hybrid architectures, API discovery ensures all endpoints across environments are identified, documented, and secured throughout the transition.
  
• Third-party API Risk Management: Organizations relying on external APIs from partners or SaaS providers use API discovery to monitor dependencies, assess security risks, and ensure proper integration of these external services.

Challenges in API Discovery

While API discovery delivers clear benefits, it also comes with challenges that organizations must address to succeed. Below are the most common obstacles to effective API discovery.

Shadow APIs and Unknown Endpoints

Shadow APIs - those deployed without IT oversight - and other undocumented endpoints are among the biggest challenges in discovery efforts. Because these APIs operate outside formal processes, they are harder to detect and can create significant blind spots in security and governance.

Lack of Documentation

Many APIs, especially in fast-paced development environments, are poorly documented or not documented at all. This makes it difficult for discovery tools to identify them accurately and for teams to understand their purpose and dependencies.

Legacy Systems and Unstandardized Interfaces

Older systems often use proprietary or outdated protocols, making it challenging for modern discovery tools to identify and interpret their APIs. Unstandardized interfaces across teams and business units compound the problem, resulting in incomplete inventories.

Scaling in Multi-Cloud or Microservices Environments

As organizations adopt microservices and multi-cloud strategies, the number of APIs increases exponentially. Managing discovery at this scale requires robust tools and processes capable of handling dynamic, distributed environments without overwhelming resources.

Limited Integration with Existing Tools

API discovery tools that do not integrate well with existing security, monitoring, and development workflows can create operational silos. Lack of integration with SIEM, IAM, or CI/CD pipelines limits the effectiveness of discovery efforts and makes it harder to act on findings.

Resource Constraints and Skill Gaps

Many organizations lack the dedicated personnel or specialized expertise to deploy, configure, and maintain API discovery tools effectively. This can lead to incomplete implementation and missed opportunities to secure and optimize the API ecosystem.

Tzvika Shneider

CEO, Pynt

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

Expert Tip: Fortify API Management with Anomaly Detection, Automation, and Segmentation

• Use anomaly detection tools for API discovery: Apply anomaly detection algorithms to monitor API traffic and highlight unusual patterns, which may reveal shadow APIs or undocumented endpoints.
• Automate API documentation updates: Integrate tools that automatically generate and update API documentation based on changes in code, ensuring accuracy and reducing the burden on developers.
• Employ network segmentation to isolate API environments: Separate API environments to minimize the risk of unauthorized access and ensure that shadow APIs or insecure endpoints don't impact critical systems.

How to Improve API Discovery: Best Practices

Adopting proven best practices helps organizations build and maintain a comprehensive and secure API inventory. Below are key practices to guide effective API discovery initiatives.

1. Monitor and Analyze Network Traffic to Discover API Calls and Patterns

Capturing and inspecting network traffic reveals active API calls and usage patterns that might otherwise go unnoticed. This method helps identify shadow and hidden APIs in production environments, ensuring they are included in the inventory.

2. Perform Static Code Analysis to Discover API Endpoints in Code

Reviewing source code allows teams to identify API endpoints defined in the application logic. Static analysis helps uncover undocumented or legacy endpoints that may never appear in runtime traffic but still pose potential risks.

3. Establish API Governance Policies

Implementing clear governance policies ensures all APIs are documented, registered, and reviewed periodically. Governance frameworks reduce duplication, enforce security standards, and keep the inventory current as APIs evolve.

4. Provide Training and Promote Awareness Among Developers and IT Staff

Educating development and operations teams on the importance of API documentation, security, and discovery fosters an API-first culture. Well-informed teams are more likely to follow policies and maintain consistent visibility across the API ecosystem.

5. Leverage API Management Platforms

Using API management platforms centralizes the control, monitoring, and documentation of APIs. These platforms often include built-in discovery capabilities, making it easier to maintain an up-to-date inventory and enforce policies at scale.

6. Incorporate Discovery into CI/CD Pipelines

Integrating API discovery into continuous integration and deployment pipelines ensures new APIs are detected, tested, and documented automatically. This prevents gaps in visibility as the application evolves and reduces the risk of shadow APIs.

7. Tag and Catalog APIs for Visibility

Applying consistent tags and maintaining a well-organized catalog of APIs improves visibility and makes it easier to manage the inventory. Tagging by purpose, sensitivity, or business unit helps teams prioritize security and operational efforts effectively.

Tools and Platforms for API Discovery

A range of tools and platforms can help organizations discover, catalog, and manage their APIs. These options fall into several categories, each with unique strengths and use cases. Below are the most common categories of API discovery solutions.

• Open Source Tools: Community-driven projects like APIClarity and OWASP Amass offer basic discovery and monitoring features. They are cost-effective and flexible but often require more manual setup and ongoing maintenance.
  
• Commercial Solutions: Platforms such as Postman, SwaggerHub, and RapidAPI deliver advanced discovery, documentation, and testing capabilities. These tools are designed for ease of use, scalability, and seamless integration with enterprise workflows.
  
• Native Cloud Provider Tools: Major cloud providers, including AWS, Google Cloud Platform, and Microsoft Azure, offer built-in discovery features through their API gateways and management consoles. These tools are ideal for organizations already invested in a specific cloud ecosystem.
  
• Third-party API Directories and Marketplaces: External directories like RapidAPI Hub or APIs.guru help organizations find and evaluate publicly available APIs for integration. These marketplaces are especially useful when sourcing third-party APIs to extend application functionality.
  
• Security-Focused API Discovery Tools: These tools are purpose-built to continuously discover and secure APIs across environments, with a strong emphasis on identifying shadow, zombie, and undocumented endpoints in production. They combine discovery, testing, and runtime monitoring to reduce security risk and improve compliance. Pynt automates the discovery of APIs, including shadow and undocumented endpoints, and performs continuous security testing to highlight vulnerabilities in real time. It integrates with CI/CD pipelines, cloud infrastructure, and SIEM tools to streamline security and compliance workflows.

Discover and Track All APIs, Automatically with Pynt

Manual methods can no longer make the cut for companies in 2025.

Leveraging an automated approach to identify internal, external, and third-party APIs, to always stay ahead of your API attack surface. 

With Pynt's API Discovery 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, many other sources, 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.
• Zombie API:  There’s an API in prod and testing, however not in API documentation.

Conclusion

API discovery is essential for securing, managing, and scaling modern application ecosystems. Identifying all APIs, including shadow, undocumented, and external endpoints, helps strengthen security, improve efficiency, and ensure compliance. Organizations can choose from manual, automated, passive, and active approaches, supported by tools like Pynt and others.

While challenges such as legacy systems and hidden endpoints persist, following best practices and using the right platforms make it possible to maintain a complete and accurate API inventory. As APIs multiply across cloud, microservices, and third-party integrations, continuous discovery remains critical to maintaining visibility and control.

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FAQs

What is REST API Discovery?

REST API discovery is the process of identifying and documenting RESTful API endpoints within an application or network. It involves scanning traffic, code, and configurations to map out all available REST APIs, including those that may be undocumented or hidden.

What is the difference between API Discovery and API management?

API discovery focuses on identifying and inventorying all APIs in use, including shadow and undocumented endpoints. API management encompasses a broader set of activities, including publishing, monitoring, securing, and controlling access to APIs throughout their lifecycle.

What is the difference between an API gateway and service discovery?

An API gateway is a centralized entry point that manages, secures, and routes API traffic. Service discovery is the process of automatically detecting available services within a dynamic environment, often used in microservices architectures to enable services to find and communicate with each other.

What is API tracing?

API tracing refers to monitoring and recording the sequence of API calls and their interactions within a system. It provides visibility into how requests are processed, helps diagnose performance issues, and aids in debugging distributed systems.

What is the difference between an API and a Web service request?

An API request is a call made to any type of application programming interface, which can include REST, GraphQL, or other protocols. A web service request specifically refers to communication over a network using standardized web protocols such as SOAP or REST.

What are the API requirements?

API requirements define the functional and non-functional expectations for an API, including its purpose, endpoints, data formats, authentication methods, rate limits, and performance criteria. Well-defined requirements ensure APIs meet business needs and integrate smoothly into existing systems.

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Learn more about API Security with these resources