PingGateway

McpValidationFilter

Validates Model Context Protocol (MCP) requests:

This feature has Evolving interface stability. It’s subject to change without notice, even in a minor or maintenance release.

  • Validates the Origin header against a list of allowed origins.

  • Validates the Accept header content types.

  • Validates the JSON-RPC format of the payload.

  • Validates the MCP client message format, excluding the tools schemas.

  • Rewrites the MCP protocol version in the initialize request to the supported version. PingGateway supports versions 2025-06-18 and 2025-11-25 (new in 2026.6).

  • Adds an McpContext for further processing.

  • Optionally records metrics for MCP requests.

If your MCP server uses server-sent events (SSE), make sure you enable streaming in PingGateway.

Usage

{
  "name": string,
  "type": "McpValidationFilter",
  "config": {
    "acceptedOrigins": [ configuration expression<pattern>, …​ ],
    "metricsEnabled": configuration expression<boolean>,
    "maxMetricParamValues": configuration expression<number>,
    "preferredServerVersion": configuration expression<string>
    }
  }
}

Properties

"acceptedOrigins": array of configuration expression<pattern>, required

Pattern or array of patterns matching the accepted origins for MCP requests.

The filter uses this for cross-origin request sharing (CORS) validation of the Origin header.

In PingGateway 2026.3 and 2026.6, the pattern isn’t anchored. Use an anchored pattern in your settings, such as "acceptedOrigins": "^https://example.com$". Don’t use a pattern like example.com alone, because that matches any origin containing example.com, including http://malicious-example.com.

"metricsEnabled": configuration expression<boolean>, optional

Whether to record metrics for MCP requests.

Default: true

"maxMetricParamValues": configuration expression<number>, optional

The maximum number of distinct tool, prompt, and resource names tracked in MCP metrics per method. Beyond this value, PingGateway groups the metrics into an "other" category.

This feature requires PingGateway 2026.9 or later.

Default: 1000

"preferredServerVersion": configuration expression<string>, optional

The preferred protocol version of the protected MCP server.

This feature requires PingGateway 2026.6 or later.

Default: the latest supported version, currently 2025-11-25

More information

org.forgerock.openig.mcp.McpValidationFilterHeaplet