MCP-REG-003

version is present and valid semver

“The MCP Registry recommends semantic versioning, but supports any version string format.” — spec anchor

How to fix this

Give `version` in `server.json` a valid semantic version string. The registry accepts any format, but semver is what its tooling and its consumers expect.

Example: failing and passing

version is a range (^1.0.0), which the registry prohibits and which is not a semantic version.

Violates MCP-REG-003 · JSON

{
  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-12-11/server.schema.json",
  "name": "com.example/weather",
  "description": "Weather forecasts for any city.",
  "version": "^1.0.0",
  "remotes": [{ "type": "streamable-http", "url": "https://mcp.example.com/mcp" }]
}

version is a plain semantic version, the format the registry recommends.

Complies with MCP-REG-003 · JSON

{
  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-12-11/server.schema.json",
  "name": "com.example/weather",
  "description": "Weather forecasts for any city.",
  "version": "1.0.0",
  "remotes": [{ "type": "streamable-http", "url": "https://mcp.example.com/mcp" }]
}

How the validator checks this

This rule is catalogued from the specification but is not yet checked automatically. No probe emits a finding for it, so it never appears in a report as pass, warn or fail. It is documented here because it is a real requirement of the specification — it is simply not one this validator can confirm for you yet.

Check your own server against MCP-REG-003

The validator does not check MCP-REG-003 automatically yet, so confirm it by hand against the examples above. It does check 73 of the 79 rules — validate a server to see those.

Background on this topic: how to publish to the official registry.