Meta extension type

Generic metadata passed with most requests.

Metadata 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: If specified, MUST be a series of labels separated by dots (.), followed by a slash (/). Labels MUST start with a letter and end with a letter or digit; interior characters can be letters, digits, or hyphens (-). Any prefix beginning with zero or more valid labels, followed by modelcontextprotocol or mcp, followed by any valid label, is reserved for MCP use. For example: modelcontextprotocol.io/, mcp.dev/, api.modelcontextprotocol.org/, and tools.mcp.com/ are all reserved.
• Name: Unless empty, MUST begin and end with an alphanumeric character ([a-z0-9A-Z]). MAY contain hyphens (-), underscores (_), dots (.), and alphanumerics in between.