Error message
When this error occurs
Everyurl under defaults.mcp_servers[] (and under config_override.mcp_servers[] on a run)
must be an absolute https:// URL with a host. The API validates this at conversation- and
run-create time, so a bad URL fails fast here rather than at run start as a
MCP Discovery Failed.
https is required because a public MCP server is called with no bearer — over plaintext http
the tool arguments (and, for a Narrative-owned server, a server-minted token) would travel in the
clear. Malformed values (no scheme, no host, or not a URL at all) are rejected for the same reason.
How to fix
Re-post the request with the corrected URLs. A URL that is well-formed but unreachable or not a
valid MCP endpoint surfaces later as MCP Discovery Failed.