docs: clarify reverse DNS namespacing rules for server names and extension metadata

docs/reference/api/openapi.yaml

@@ -778,7 +778,7 @@ components:
       properties:
         name:
           type: string
-          description: "Server name in reverse-DNS format. Must contain exactly one forward slash separating namespace from server name."
+          description: "Unique MCP server identifier in reverse-DNS format. Must contain exactly one forward slash separating namespace from the server name. Include as many subdomain levels in the namespace as necessary for uniqueness."
           example: "io.github.user/weather"
           minLength: 3
           maxLength: 200
@@ -828,7 +828,7 @@ components:
             $ref: '#/components/schemas/RemoteTransport'
         _meta:
           type: object
-          description: "Extension metadata using reverse DNS namespacing for vendor-specific data"
+          description: "Optional extension metadata for vendor-specific data. Keys must use reverse-DNS namespacing to avoid collisions. Include as many subdomain levels as necessary for uniqueness."
           properties:
             io.modelcontextprotocol.registry/publisher-provided:
               type: object

docs/reference/server-json/generic-server-json.md

@@ -30,6 +30,13 @@ The optional `_meta` field allows publishers to include custom metadata alongsid
 
 When publishing to the official registry, custom metadata must be placed under the key `io.modelcontextprotocol.registry/publisher-provided`. See the [official registry requirements](./official-registry-requirements.md) for detailed restrictions and examples.
 
+## Reverse DNS Namespacing
+
+Both the `_meta` keys and the `name` field in a `server.json` file use reverse DNS format to provide a structured, globally unique namespace.
+
+Reverse DNS components (including subdomains) MAY be included as necessary for uniqueness.
+There is no fixed limit on the number of domain segments, as long as the namespace is derived from a domain name controlled by the publisher.
+
 ## Examples
 
 <!-- As a heads up, these are used as part of tests/integration/main.go -->

docs/reference/server-json/server.schema.json

@@ -409,7 +409,7 @@
           "type": "string"
         },
         "_meta": {
-          "description": "Extension metadata using reverse DNS namespacing for vendor-specific data",
+          "description": "Optional extension metadata for vendor-specific data. Keys must use reverse-DNS namespacing to avoid collisions. Include as many subdomain levels as necessary for uniqueness.",
           "properties": {
             "io.modelcontextprotocol.registry/publisher-provided": {
               "additionalProperties": true,
@@ -443,7 +443,7 @@
           "type": "array"
         },
         "name": {
-          "description": "Server name in reverse-DNS format. Must contain exactly one forward slash separating namespace from server name.",
+          "description": "Unique MCP server identifier in reverse-DNS format. Must contain exactly one forward slash separating namespace from the server name. Include as many subdomain levels in the namespace as necessary for uniqueness.",
           "example": "io.github.user/weather",
           "maxLength": 200,
           "minLength": 3,