Source note · Model Context Protocol transports compared
In Streamable HTTP under MCP revision 2026-07-28, every POST to the MCP endpoint MUST include an MCP-Protocol-Version header whose value MUST match the io.modelcontextprotocol/protocolVersion field in the request body's _meta; on mismatch the server MUST reject with 400 Bad Request and a HeaderMismatch JSON-RPC error.
Checked 2026-09-30
- Vendor
- Model Context Protocol project
- Product
- MCP specification
- Subsystem
- request metadata
- Deployment
- remote-http
- Region
- not restricted
- Release range
- MCP revision 2026-07-28
- Checked
- 2026-09-30
Sources
- Model Context Protocol specification 2026-07-28, Streamable HTTP — Model Context Protocol project · tier 1 standards and regulators · section Request Metadata, subsection Protocol Version Header, first three paragraphs
Cite this note
APA
WarmTransfer. (2026, September 30). Model Context Protocol transports compared: source note mcp-transport-differences-http-version-header. WarmTransfer. https://warmtransfer.net/knowledge/claims/mcp-transport-differences-http-version-header
BibTeX
@misc{warmtransfer-claim-mcp-transport-differences-http-version-header,
title = {Model Context Protocol transports compared: source note mcp-transport-differences-http-version-header},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/mcp-transport-differences-http-version-header},
note = {Source note mcp-transport-differences-http-version-header, checked 2026-09-30}
}