Both sit at the MCP boundary and proxy multiple servers, but they answer different questions. Lasso asks what is inside this request or response, and is the payload or the server itself dangerous. PolicyLayer asks whether this person may call this tool with these arguments right now. For most teams the honest answer is that they are complementary. Here is where each one fits.
Lasso does content inspection and supply-chain scanning, much of it self-hosted and free. PolicyLayer does fleet-wide deterministic access governance. Different jobs at the same boundary.
PolicyLayer is the hosted gateway your MCP traffic runs through. Connect your servers and every tool call is checked against deterministic, deny-by-default policy before it executes: allow, deny, rate-limit, or require approval, with argument-level rules, per-person scoped tokens, and one unified audit log across every client and server. Recommended policy ships pre-classified across 220,000+ catalogued tools.
Lasso Security's MCP Gateway is an open-source (MIT), self-hosted proxy that inspects the content of MCP traffic. Its plugins mask secrets and tokens, detect and anonymise PII with Microsoft Presidio, and filter prompt injection and harmful content, with an advanced natural-language policy tier backed by Lasso's cloud. It also scores server reputation from marketplace and GitHub data and detects hidden instructions in tool descriptions before a server loads. Lasso is a 2024 Gartner Cool Vendor for AI Security, with a wider GenAI security platform.
Content security and supply-chain scanning, versus deterministic access governance.
| PolicyLayer | Lasso Security | |
|---|---|---|
| Primary job | Decide whether a call is allowed, deterministically, before it runs | Inspect and sanitise payload content, and score server trustworthiness |
| Enforcement model | Deterministic, rule-based, deny by default | Content inspection and masking; advanced policy is natural-language and cloud-backed |
| Granularity | Per tool and per argument (allow refund_payment only when amount is under $100) | Content-level: masks secrets and PII, filters injection; no argument-level allow or deny |
| Supply-chain scanning | Per-tool risk classification across the catalogue | Pre-load reputation scoring and hidden-instruction detection; can auto-block low-reputation servers |
| Approvals | Human approval gates on any call | Not a documented primitive in the open-source gateway |
| Identity | Per-person scoped grant tokens, attributable across a team | Single-user local proxy in the open-source form; no per-person isolation |
| Scope | Multi-client, multi-person control plane across the fleet | Local developer tool (Cursor, Claude Desktop) in the open-source gateway |
| Audit | One unified log across every client and server, tied to per-call decisions | Per-guardrail and local logging; the paid platform adds a dashboard |
| Deployment | Hosted control plane; nothing to run | Open-source (MIT), self-hosted via pip or Docker, no cloud dependency for core plugins |
| Best fit | Deterministic access governance across a fleet | Free, self-hosted content security and server reputation scanning |
Same inputs, same decision, every time, attributable to a person, in one log: deny a refund over a limit, require approval, block a destructive call.
Many AI clients and many people route through one plane, with the same policy holding across every client and server.
Deny on the value an agent passes, not just the tool it calls, and pause sensitive calls for human sign-off.
Recommended rules pre-classified across 220,000+ tools, with per-tool risk built in.
You need to mask secrets and PII and filter prompt injection in request and response content itself.
Full local control with no vendor in the path and no licensing cost for the core plugins.
Pre-load scoring of community servers and detection of hidden instructions in tool descriptions before a server loads.
These are largely complementary. A sensible architecture runs Lasso to mask secrets and catch injection in the payload, and PolicyLayer to decide whether the call is permitted and record it across the fleet. Lasso's paid platform adds runtime enforcement at the proxy layer, where the access-governance overlap grows, but it is positioned as broad GenAI security rather than MCP-fleet-specific deterministic per-call policy.
Whatever your agents touch, the same engine, audit, and access model is doing the work underneath every rule you write.
Rules run as code, not model judgement: argument-level conditions, quotas, deny-by-default. The same call gets the same decision every time.
Writing policies →Your security or compliance team writes and attaches policy without ever holding the upstream credentials or grant tokens.
Roles →Every call is logged with its decision and the rule that fired, attributed to the identity, in an append-only record. Argument values are redacted, never stored.
Logs & security →Upstream secrets are encrypted at rest and injected by the gateway. The agent only ever holds a scoped token.
Logs & security →Every person and agent connects with its own scoped grant. Rotate or revoke any one of them instantly, without disrupting the rest.
Core concepts →Hosted gateway. Point your clients at it, register a server, issue a token. Nothing to install.
Quick start →Not in the payload-inspection sense. PolicyLayer can redact fields from tool results, but its focus is the deterministic allow or deny decision on the call. Lasso's open-source gateway focuses on masking secrets and PII and filtering injection in content.
They sit at the same boundary but answer different questions. Lasso inspects what is inside the request or response; PolicyLayer decides whether the call is permitted, on its arguments, and records it across the fleet.
No. PolicyLayer is a hosted control plane. Lasso's open-source MCP Gateway is MIT-licensed and self-hostable, which is a genuine point in its favour if running entirely on your own infrastructure is a hard requirement.
Yes. Run Lasso on content and supply-chain risk, and PolicyLayer on deterministic per-call access governance and fleet audit.
Deterministic, deny-by-default policy on every MCP tool call: approval gates, per-identity scopes, argument-level rules, and one unified audit log. Route your existing MCP servers through the gateway, live in minutes.
Instant setup, no code required.