// GLOSSARY -- POLICY ENFORCEMENT

What is Fail-Closed Enforcement?

1 min read Updated

A security posture where tool calls are blocked by default when the policy engine or proxy is unavailable, ensuring that enforcement failures never result in unauthorised actions.

WHY IT MATTERS

In distributed systems, components fail. Networks drop. Services crash. When the policy enforcement layer fails, there are two choices: fail open (allow everything) or fail closed (block everything).

Fail-closed is the only safe default for AI agent enforcement. An agent with no policy is an agent with no limits. If the proxy is down, agents can't act — safety over availability.

Fail-Closed Enforcement isn't theory — define it as policy in PolicyLayer and it's enforced on every tool call.

ENFORCE THIS WITH POLICY →

Enforced before the call runs. Nothing to install.

HOW POLICYLAYER USES THIS

PolicyLayer is fail-closed by design. If the proxy is unreachable, MCP tool calls cannot reach the upstream server. This is PolicyLayer's core safety guarantee.

Read the policy-writing guide →

FURTHER READING

// THE REGISTRY

Every MCP server your agents touch has a registry record.

Type a name, get the breakdown: verified identity, auth posture, risk grade, every tool classified, recommended policy. Re-checked continuously.

Teams ship this data inside their own products. See what a licence covers →

Take your agents live. Without losing control.

Route your MCP traffic through PolicyLayer. Every tool call is checked against your policy before it runs: allow, deny, or require approval. Per-identity grants. Full audit log. Live in minutes.

ENFORCE THIS WITH POLICY →

Instant setup, no code required.

46,500+ MCP servers and 515,000+ tools scanned and risk-classified.

// GET IN TOUCH

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