icons[].src is https: or data:, same-origin, no unsafe scheme

How to fix this

Serve icon URIs over `https:` or inline as `data:`, from the same origin as the server. A conformant client rejects any other scheme, and follows no redirects to reach one.

How the validator checks this

Probe P2.1, against a streamable-http server on the modern protocol. What it reports:

pass

All … advertised icon URI… use https: or data: and are same-origin with the server

fail

Icon URIs a conformant client must reject — …${problems.length > 3 ?

skip

This server advertises no icons, so there is no icon URI to check

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-HDR-008, MCP-HDR-009, MCP-RES-003, MCP-RES-006, MCP-RES-007, MCP-ERR-003, MCP-ERR-004, MCP-ERR-005, MCP-ERR-008, MCP-CAC-001, MCP-CAC-002, MCP-CAC-003, MCP-CAC-004, MCP-CAC-005, MCP-SCH-001, MCP-SCH-002, MCP-SCH-003, MCP-SCH-004, MCP-SCH-005, MCP-SCH-006, MCP-SCH-007, MCP-SEC-005, MCP-SEC-006, MCP-DEP-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 Security posture rules

• MCP-SEC-001Invalid Origin header returns HTTP 403
• MCP-SEC-002Endpoint is HTTPS with a valid, unexpired certificate chain
• MCP-SEC-003Error messages do not echo request headers or credentials
• MCP-SEC-005No $ref in tool schemas resolves to a network URI
• MCP-SEC-006Schema depth and subschema count stay within safe bounds
• MCP-SEC-007Server does not reflect the Authorization header into responses