Whether a _meta key's prefix is reserved for MCP use under the effective
protocol version v. The two revisions differ:
- 2025-06-18 (basic/index): "Any prefix beginning with zero or more valid
labels, followed by modelcontextprotocol or mcp, followed by any valid
label, is reserved." So the mcp-token may appear in ANY position as long as
at least one more label follows it — e.g. modelcontextprotocol.io/,
mcp.dev/, api.modelcontextprotocol.org/, and tools.mcp.com/ are all
reserved. Earlier versions (2024-11-05, 2025-03-26) had no formal _meta
reserved-prefix rule; this same any-position rule is applied to them as a
safe superset.
- 2025-11-25 / draft: the narrower "second label" rule (see the
single-argument overload), where com.example.mcp/ is NOT reserved.
Whether a _meta key's prefix is reserved for MCP use under the effective protocol version v. The two revisions differ:
- 2025-06-18 (basic/index): "Any prefix beginning with zero or more valid labels, followed by modelcontextprotocol or mcp, followed by any valid label, is reserved." So the mcp-token may appear in ANY position as long as at least one more label follows it — e.g. modelcontextprotocol.io/, mcp.dev/, api.modelcontextprotocol.org/, and tools.mcp.com/ are all reserved. Earlier versions (2024-11-05, 2025-03-26) had no formal _meta reserved-prefix rule; this same any-position rule is applied to them as a safe superset. - 2025-11-25 / draft: the narrower "second label" rule (see the single-argument overload), where com.example.mcp/ is NOT reserved.