Nexus AI Security
The Authorization Layer for
AI Agents
AI agents are now calling your tools, moving your data, and triggering real workflows. Nexus Security Proxy sits in front of your MCP servers to enforce policy-driven authorization, payload validation, and governance before any action is executed.
AI Agents Are the New Identity.
Who’s Authorizing Them?
We’ve learned how to secure users, devices, and applications. But AI agents don’t fit neatly into any of those categories:
- They don’t sign in through Okta or Azure AD.
- They don’t have HR records, onboarding, or offboarding.
- Yet they can move money, query sensitive data, and call internal tools via MCP and APIs.
Most AI stacks today rely on basic checks:
If the API key works, the call goes through.
If the model is fine-tuned, we assume it’s safe.
If the agent runs, we hope it stays within its lane.
Hope is not policy.
Enterprises need a reliable authorization layer that decides what AI agents are allowed to do—not just whether they can connect.
A Gatekeeper for AI Agents and MCP Tool Calls
Nexus Security Proxy is a lightweight, high-performance gateway that sits in front of your Model Context Protocol (MCP) servers. It evaluates every request from AI agents and clients, then decides whether to:
The call proceeds normally.
The call is blocked immediately.
The payload is modified before execution.
Key Outcomes
Nexus brings Zero Trust principles to AI by treating every agent-to-tool call as an authorization decision.
Designed for AI-Forward, Security-Critical Organizations
AI Platform & Engineering Teams
- • Safely expose internal tools to AI agents.
- • Standardize authorization logic instead of reinventing it in every MCP server.
Security & IAM Teams
- • Extend Zero Trust to AI and non-human identities.
- • Separate security policy from application code.
- • Gain audit trails for every AI-driven action.
Risk, Compliance & Governance
- • Understand what agents can access and do.
- • Support AI-related controls for regulations and audits.
What Nexus Security Proxy Delivers
4.1 Policy-as-Code Authorization
Define policies in YAML or Rego.
Governs:
- Which agents/users call which tools
- Allowed MCP methods (call_tool, read_resource)
- Conditions (role, tenant, env, IP)
- role: support_agent
allow: [tickets.search, tickets.comment]
- role: admin
allow: [tickets.delete]
4.2 Payload-Aware Enforcement (ABAC)
Go beyond “who can call what” into “what can be sent”.
Capabilities
- Enforce numeric thresholds (amount, rows)
- Restrict sensitive fields (PII, PHI)
- Business rule validation
Example Rules
Allow payments.transfer only if amount < 10,000 for non-admins.
Deny export calls with row_count > 5,000 unless role = DataAdmin.
4.3 JSON Schema Validation
Nexus validates payloads against tool-specific JSON Schemas, rejecting malformed parameters to protect tools from injection.
4.4 Identity & Context-Aware
Integrates with JWTs, mTLS, or API keys. Extracts subject, roles, tenant, and environmental context (IP, region) for decisions.
4.5 Centralized Audit
Every decision (ALLOW/DENY) is logged with Who, What, Why, and Result. Exports directly to Splunk, Datadog, or ELK.
Built to Complement, Not Replace, Your MCP Servers
MCP servers manage tool definitions. Nexus manages authorization. It provides a single control layer across multiple servers and tools.
Flexible Deployment for Modern AI Platforms
Reverse Proxy
Recommended to StartNexus terminates TLS and forwards to MCP server. Ideal for PoCs and rapid pilots.
Sidecar Mode
KubernetesNexus runs alongside MCP in the same pod. Enforces authorization locally for each server instance.
Service Mesh
Envoy / IstioNexus runs as an ext_authz service. Centralizes authorization across services and clusters.
Performance Targets
Real-World Scenarios Nexus Secures
Financial Transactions
Agents initiate payments or refunds. Nexus limits amounts, enforces dual-control for large transfers, and blocks unapproved accounts.
Sensitive Data Queries
Agents query customer records or health data. Nexus enforces which agents can see which datasets, and under what filters.
DevOps & Internal Tools
Agents trigger build or diagnostic tools. Nexus scopes which environments and commands are allowed from which agents.
Starting with Authorization.
Growing into Full AI Governance.
Near-Term Enhancements
- Adaptive and context-based risk scoring
- Optional step-up (MFA/Approval) for high-risk actions
- Shadow mode for policy testing
Long-Term Vision
- AI identity lifecycle management
- Access reviews for AI agents
- Behavior analytics & anomaly detection
- Data boundary and DLP integrations
Why an Authorization Proxy is the Right Primitive
Instead of hardcoding RBAC and business rules into each MCP server, enterprises gain a shared control plane that can evolve as AI usage grows.
Frequently Asked Questions
We already have an MCP server with some RBAC. Why do we need this?
MCP RBAC is typically scoped to a single server and doesn’t handle payload policies, multi-environment governance, or centralized audit. Nexus gives you a cross-platform authorization fabric for all AI agents and servers.
Does this slow down our AI workloads?
Nexus is optimized for low-latency authorization. Policies are evaluated in-memory, with sub-25ms p95 targets, and the design is fully stateless for horizontal scaling.
Do we need to modify our AI agents or MCP servers?
In most cases, no. Nexus can run as a reverse proxy with no changes, making adoption quick and low-risk.
Secure Your AI Agents Before They Scale
AI is moving from experiments to production. Now is the time to put a real authorization layer in place—before agents gain access to critical systems without guardrails.
