null
.result
or an error
MUST be set. A response MUST NOT
set both._meta
_meta
property/parameter is reserved by MCP to allow clients and servers
to attach additional metadata to their interactions.
Certain key names are reserved by MCP for protocol-level metadata, as specified below;
implementations MUST NOT make assumptions about values at these keys.
Additionally, definitions in the schema
may reserve particular names for purpose-specific metadata, as declared in those definitions.
Key name format: valid _meta
key names have two segments: an optional prefix, and a name.
Prefix:
.
), followed by a slash (/
).
-
).modelcontextprotocol
or mcp
, followed by any valid label,
is reserved for MCP use.
modelcontextprotocol.io/
, mcp.dev/
, api.modelcontextprotocol.org/
, and tools.mcp.com/
are all reserved.[a-z0-9A-Z]
).-
), underscores (_
), dots (.
), and alphanumerics in between.