Source note · Model Context Protocol transports compared
In MCP revision 2026-07-28, clients using Streamable HTTP MUST support x-mcp-header annotations, mirroring designated tool parameter values into Mcp-Param-{name} headers and excluding from tools/list results any tool whose annotation violates the constraints, whereas clients using other transports such as stdio MAY ignore x-mcp-header annotations entirely.
Checked 2026-09-30
Clients using other transports (e.g., stdio) **MAY** ignore `x-mcp-header` annotations entirely.
- Vendor
- Model Context Protocol project
- Product
- MCP specification
- Subsystem
- request metadata
- Deployment
- local-subprocess, 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 Custom Headers from Tool Parameters, and Schema Extension final paragraph
Cite this note
APA
WarmTransfer. (2026, September 30). Model Context Protocol transports compared: source note mcp-transport-differences-x-mcp-header-scope. WarmTransfer. https://warmtransfer.net/knowledge/claims/mcp-transport-differences-x-mcp-header-scope
BibTeX
@misc{warmtransfer-claim-mcp-transport-differences-x-mcp-header-scope,
title = {Model Context Protocol transports compared: source note mcp-transport-differences-x-mcp-header-scope},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/mcp-transport-differences-x-mcp-header-scope},
note = {Source note mcp-transport-differences-x-mcp-header-scope, checked 2026-09-30}
}