MCP-DEP-004
No legacy HTTP+SSE endpoint is served
“New implementations SHOULD NOT adopt it; existing implementations SHOULD migrate to Streamable HTTP.” — spec anchor
How to fix this
Stop serving the legacy HTTP+SSE endpoint and migrate to Streamable HTTP. New implementations should not adopt the old transport at all.
How the validator checks this
Probe P5.1, against a streamable-http server on the modern / legacy / dual protocol. What it reports:
- pass
- No legacy HTTP+SSE stream served on GET
- warn
- GET returned text/event-stream — that is the deprecated HTTP+SSE transport; new implementations should not adopt it
Quoted from the probe that runs this check, so it cannot drift from what the validator actually reports.
This rule is checked deterministically: a fail here is a certain violation, not an inference.
Checked in the same request as MCP-STL-005.
Check your own server against this rule
The validator makes real protocol requests and reports this rule as pass, warn or fail alongside the other 78. Validate a server or read how the check works.
Other Deprecated and removed features rules
- MCP-DEP-001ping is no longer implemented
- MCP-DEP-002logging/setLevel is no longer implemented
- MCP-DEP-003resources/subscribe and resources/unsubscribe replaced by subscriptions/listen
- MCP-DEP-005Roots / Sampling / Logging capabilities are not advertised
- MCP-DEP-006Server accepts initialize (dual-era support)
- MCP-DEP-007A modern-only server names its supported versions in the initialize error