MCP 2025-06-18
SUPERSEDED Confidence: High (1.00)MCP 2025-06-18 is a superseded revision of the Model Context Protocol specification, released 2025-06-18.
What is MCP specification revision 2025-06-18?
MCP 2025-06-18 is a superseded revision of the Model Context Protocol specification, released 2025-06-18.
Removed JSON-RPC batching, added structured tool output and elicitation, classified MCP servers as OAuth resource servers, and required RFC 8707 resource indicators plus the MCP-Protocol-Version header on HTTP.
What changed in MCP 2025-06-18?
- Removed JSON-RPC batching support
- Structured tool output
- MCP servers classified as OAuth resource servers with protected resource metadata
- Clients required to implement RFC 8707 resource indicators against malicious-server token capture
- Elicitation - servers can request additional information from users
- Resource links in tool call results
- MCP-Protocol-Version header required on subsequent HTTP requests
MCP 2025-06-18 hardened the authorization story (resource-server classification, RFC 8707 resource indicators) and introduced elicitation, structured tool output, and resource links. It also removed the JSON-RPC batching added in the previous revision and made the MCP-Protocol-Version HTTP header mandatory after negotiation.
How was this verified, and what are the sources?
Verified · method: spec-changelog
· confidence 1.00 (High).