MCP schema drift compatibility — MCPDriftVerdict

Expected input

{"type":"object","required":["contract_version","subject","annotation_source_trust","baseline","current"],"additionalProperties":false,"properties":{"contract_version":{"type":"string","const":"mcp-drift/1"},"subject":{"type":"object","description":"Stable caller-chosen server identity.","additionalProperties":true},"annotation_source_trust":{"type":"string","enum":["trusted","untrusted"]},"baseline":{"type":"object","description":"Complete baseline tools/list snapshot.","additionalProperties":true},"current":{"type":"object","description":"Complete current tools/list snapshot.","additionalProperties":true}}}

What it returns

{"type":"object","properties":{"service":{"type":"string","const":"MCPDriftVerdict"},"contract_version":{"type":"string","const":"mcp-drift/1"},"ruleset_version":{"type":"string","const":"2026-07-20.1"},"subject":{"type":"object","properties":{"server_id":{"type":"string"},"identity":{"type":"string","const":"caller_asserted"}},"required":["server_id","identity"],"additionalProperties":false},"verdict":{"type":"string","enum":["UNCHANGED","SAFE_ADDITIVE","REVIEW","INCONCLUSIVE","BREAKING","SECURITY_REGRESSION"]},"action":{"type":"string","enum":["ACCEPT_CURRENT","REVIEW_CURRENT","HOLD_BASELINE","BLOCK_CURRENT"]},"trust":{"type":"object","properties":{"annotation_source":{"type":"string","enum":["caller_asserted_trusted","untrusted"]},"server_identity":{"type":"string","const":"not_verified"},"runtime_behavior":{"type":"string","const":"not_verified"},"completeness":{"type":"string","const":"caller_asserted"}},"required":["annotation_source","server_identity","runtime_behavior","completeness"],"additionalProperties":false},"hashes":{"type":"object","properties":{"baseline_snapshot":{"type":"string","pattern":"^sha256:[a-f0-9]{64}$"},"current_snapshot":{"type":"string","pattern":"^sha256:[a-f0-9]{64}$"},"baseline_contract":{"type":"string","pattern":"^sha256:[a-f0-9]{64}$"},"current_contract":{"type":"string","pattern":"^sha256:[a-f0-9]{64}$"}},"required":["baseline_snapshot","current_snapshot","baseline_contract","current_contract"],"additionalProperties":false},"summary":{"type":"object","properties":{"baseline_tools":{"type":"integer","minimum":0},"current_tools":{"type":"integer","minimum":0},"added":{"type":"integer","minimum":0},"removed":{"type":"integer","minimum":0},"changed":{"type":"integer","minimum":0},"compatible_changes":{"type":"integer","minimum":0},"review_findings":{"type":"integer","minimum":0},"breaking_findings":{"type":"integer","minimum":0},"security_findings":{"type":"integer","minimum":0},"unknown_relations":{"type":"integer","minimum":0}},"required":["baseline_tools","current_tools","added","removed","changed","compatible_changes","review_findings","breaking_findings","security_findings","unknown_relations"],"additionalProperties":false},"findings":{"type":"array","maxItems":256,"items":{"type":"object","properties":{"id":{"type":"string","pattern":"^sha256:[a-f0-9]{64}$"},"category":{"type":"string"},"severity":{"type":"string","enum":["info","review","breaking","security"]},"tool":{"type":["string","null"]},"path":{"type":"string"},"relation":{"type":"string","enum":["PROVEN_SUBSET","PROVEN_NOT_SUBSET","UNKNOWN","NOT_APPLICABLE"]},"before_hash":{"type":"string","pattern":"^sha256:[a-f0-9]{64}$"},"after_hash":{"type":"string","pattern":"^sha256:[a-f0-9]{64}$"},"before":{},"after":{},"witness":{},"witness_hash":{"type":"string","pattern":"^sha256:[a-f0-9]{64}$"},"reason":{"type":"string"}},"required":["id","category","severity","tool","path","relation","reason"],"additionalProperties":false}},"coverage":{"type":"object","properties":{"compared_tools":{"type":"integer","minimum":0},"schema_nodes":{"type":"integer","minimum":0},"relation_checks":{"type":"integer","minimum":0},"proven_subset":{"type":"integer","minimum":0},"proven_not_subset":{"type":"integer","minimum":0},"unknown":{"type":"integer","minimum":0},"returned_findings":{"type":"integer","minimum":0},"total_findings":{"type":"integer","minimum":0},"truncated":{"type":"boolean"}},"required":["compared_tools","schema_nodes","relation_checks","proven_subset","proven_not_subset","unknown","returned_findings","total_findings","truncated"],"additionalProperties":false},"limitations":{"type":"array","items":{"type":"string"}},"service_reuse":{"type":"string","const":"Call MCPDriftVerdict after every notifications/tools/list_changed, at agent startup when the current tools/list snapshot hash differs from the pinned baseline, and before accepting an MCP server upgrade. Reuse only for the exact baseline_snapshot hash, current_snapshot hash, and ruleset_version tuple."}},"required":["service","contract_version","ruleset_version","subject","verdict","action","trust","hashes","summary","findings","coverage","limitations","service_reuse"],"additionalProperties":false}