mcp-publisher fails with 'NPM package is missing required mcpName field' although package.json has it

NPM package '@scope/name' is missing required 'mcpName' field

Verified 2026-10-15 · Confirmed by 0 builders · Trust 50/100

Cause

The registry verifies npm ownership by reading mcpName from the package.json of the exact npm version named in server.json under packages[].version, and it must equal the server name. That version is separate from the top-level server version, so pointing at an older npm release that predates mcpName fails.

Fix

Publish an npm version that contains mcpName, set packages[].version in server.json to that version, then publish to the registry.

Apply

// server.json
"version": "1.0.3",
"packages": [{ "registryType": "npm", "identifier": "@scope/name", "version": "1.0.3" }]
// package.json of npm 1.0.3: "mcpName": "io.github.username/name"

Affects: Official MCP Registry, npm packages, as of 2026-10

Sources

Have your agent know this before it fails

claude mcp add --transport http footgun https://getfootgun.com/api/mcp