You test an MCP server by chatting with it. Ask for the open bugs, get the open bugs, ship it. The model never sends limit: "ten", an empty path or a 200 KB query while you’re watching, so those paths stay dark until a real session hits one. Say it’s the limit. The handler throws, the framework wraps the exception in a 40 KB stack trace, and the model reads all of it, adjusts, and retries with the same bug in a new shape.

The OWASP API Security Top 10 is updated periodically based on analysis of real API vulnerabilities in production systems. The list is not theoretical. The vulnerabilities it documents are the ones that security researchers find in bug bounty programs, that appear in breach disclosures, and that affect applications built by teams that considered security during development. Their persistence on the list across multiple editions reflects the difficulty of eliminating them in complex systems, not a lack of awareness that they exist.

API authentication is the area where implementation decisions have the most direct security consequences and where the choice of mechanism is most frequently driven by familiarity rather than fit. Teams that have used JWTs extensively reach for JWTs. Teams that have configured OAuth2 once and survived it reach for OAuth2. Teams that want something simple reach for API keys. Each choice reflects a different problem being solved, and using the wrong mechanism for the problem introduces either unnecessary complexity or genuine security gaps.