Fastmail — the complete, unedited output of the deterministic mcptrustchecker engine v1.13.0, scanned . Every finding, capability tag and score component below is exactly what the engine produced — no AI, no post-processing.
{
"tool": {
"name": "mcptrustchecker",
"version": "1.13.0",
"methodologyVersion": "mcptrustchecker-1.13"
},
"target": {
"id": "@jordonh19/fastmail-mcp-server",
"source": {
"kind": "package",
"origin": "@jordonh19/fastmail-mcp-server"
},
"server": {
"name": "@jordonh19/fastmail-mcp-server"
}
},
"grade": "A",
"score": {
"score": 97,
"threatScore": 100,
"grade": "A",
"band": "A",
"categorySubtotals": {
"injection": 0,
"exfiltration": 0,
"permissions": 0,
"supply-chain": 0,
"network": 0,
"hygiene": 0
},
"vector": [
{
"kind": "client",
"term": "capability-exposure",
"level": "moderate",
"label": "capability blast radius (moderate) — client exposure if the model is manipulated",
"appliedPenalty": 3
},
{
"kind": "client",
"term": "verification-discount",
"level": "source",
"label": "publisher verification (provenance) — cryptographic build provenance ties the artifact to its source",
"appliedPenalty": 0
},
{
"kind": "client",
"term": "coverage-honesty",
"level": "source",
"label": "inspection depth (source) — how much of the target the scan could see",
"appliedPenalty": 0
}
],
"gatesFired": [],
"methodologyVersion": "mcptrustchecker-1.13"
},
"capability": {
"level": "moderate",
"reasons": [
"ingests untrusted external content (a prompt-injection entry point)",
"can send data / act on an external service"
],
"tags": [
"untrusted-input",
"external-sink"
]
},
"coverage": {
"level": "source",
"inputs": {
"toolSurface": true,
"implementationSource": true,
"packageMetadata": true,
"liveTransport": false
},
"caveats": [
"Tools were statically extracted from the published source (47 recovered), not enumerated from a running server. Tool-poisoning, Unicode-smuggling, capability and toxic-flow analysis ran on this inferred surface, but a mis-parsed registration could be missed or mis-attributed, so tool-derived findings are capped below “confirmed”. To grade the real runtime surface, scan the running server: --command \"npx -y <package>\"."
]
},
"findings": [
{
"ruleId": "MTC-FLOW-005",
"title": "Untrusted input can drive an external action",
"category": "exfiltration",
"severity": "medium",
"confidence": "strong",
"description": "Untrusted-input tools ([mark_mailbox_read, search_emails, get_unread_emails, get_email_attachments, download_attachment]) co-exist with external-action tools ([send_email, forward_email]). A prompt injection could cause unwanted external actions, though no direct sensitive-data leak path was found.",
"remediation": "Require confirmation for state-changing/egress actions triggered after processing untrusted content.",
"location": {
"kind": "flow",
"name": "mark_mailbox_read → send_email"
},
"evidence": "untrusted [mark_mailbox_read, search_emails, get_unread_emails, get_email_attachments, download_attachment] → sinks [send_email, forward_email]",
"owasp": "LLM06:2025 Excessive Agency",
"references": [],
"data": {
"untrusted": [
"mark_mailbox_read",
"search_emails",
"get_unread_emails",
"get_email_attachments",
"download_attachment"
],
"sinks": [
"send_email",
"forward_email"
]
}
}
],
"toxicFlows": [
{
"id": "flow-1",
"severity": "medium",
"confidence": "strong",
"untrustedInput": [
"mark_mailbox_read",
"search_emails",
"get_unread_emails",
"get_email_attachments",
"download_attachment"
],
"sensitiveSource": [],
"externalSink": [
"send_email",
"forward_email"
],
"selfContained": false,
"description": "Untrusted input can drive an external action even though no sensitive source is exposed."
}
],
"capabilities": [
{
"tool": "list_calendars",
"tags": [],
"reasons": {}
},
{
"tool": "get_calendar_events",
"tags": [],
"reasons": {}
},
{
"tool": "get_calendar_event",
"tags": [],
"reasons": {}
},
{
"tool": "create_calendar_event",
"tags": [],
"reasons": {}
},
{
"tool": "update_calendar_event",
"tags": [],
"reasons": {}
},
{
"tool": "delete_calendar_event",
"tags": [],
"reasons": {}
},
{
"tool": "list_address_books",
"tags": [],
"reasons": {}
},
{
"tool": "search_contacts",
"tags": [],
"reasons": {}
},
{
"tool": "get_contact",
"tags": [],
"reasons": {}
},
{
"tool": "create_contact",
"tags": [],
"reasons": {}
},
{
"tool": "delete_contact",
"tags": [],
"reasons": {}
},
{
"tool": "update_contact",
"tags": [],
"reasons": {}
},
{
"tool": "check_function_availability",
"tags": [],
"reasons": {}
},
{
"tool": "move_email",
"tags": [],
"reasons": {}
},
{
"tool": "add_labels",
"tags": [],
"reasons": {}
},
{
"tool": "remove_labels",
"tags": [],
"reasons": {}
},
{
"tool": "update_email_flags",
"tags": [],
"reasons": {}
},
{
"tool": "delete_email",
"tags": [],
"reasons": {}
},
{
"tool": "bulk_email_action",
"tags": [],
"reasons": {}
},
{
"tool": "bulk_add_labels",
"tags": [],
"reasons": {}
},
{
"tool": "bulk_remove_labels",
"tags": [],
"reasons": {}
},
{
"tool": "archive_email",
"tags": [],
"reasons": {}
},
{
"tool": "mark_mailbox_read",
"tags": [
"untrusted-input"
],
"reasons": {
"untrusted-input": [
"keyword \"read_email\""
]
}
},
{
"tool": "get_mailbox_stats",
"tags": [],
"reasons": {}
},
{
"tool": "get_account_summary",
"tags": [],
"reasons": {}
},
{
"tool": "search_emails",
"tags": [
"untrusted-input"
],
"reasons": {
"untrusted-input": [
"keyword \"read_email\""
]
}
},
{
"tool": "get_email",
"tags": [],
"reasons": {}
},
{
"tool": "get_email_headers",
"tags": [],
"reasons": {}
},
{
"tool": "one_click_unsubscribe",
"tags": [],
"reasons": {}
},
{
"tool": "get_thread",
"tags": [],
"reasons": {}
},
{
"tool": "get_unread_emails",
"tags": [
"untrusted-input"
],
"reasons": {
"untrusted-input": [
"keyword \"read_email\""
]
}
},
{
"tool": "get_latest_emails",
"tags": [],
"reasons": {}
},
{
"tool": "get_mailbox_emails",
"tags": [],
"reasons": {}
},
{
"tool": "get_email_attachments",
"tags": [
"untrusted-input"
],
"reasons": {
"untrusted-input": [
"keyword \"download\""
]
}
},
{
"tool": "download_attachment",
"tags": [
"untrusted-input"
],
"reasons": {
"untrusted-input": [
"keyword \"download\""
]
}
},
{
"tool": "send_email",
"tags": [
"external-sink"
],
"reasons": {
"external-sink": [
"keyword \"send_email\""
]
}
},
{
"tool": "reply_email",
"tags": [],
"reasons": {}
},
{
"tool": "forward_email",
"tags": [
"external-sink"
],
"reasons": {
"external-sink": [
"keyword \"forward_email\""
]
}
},
{
"tool": "create_draft",
"tags": [],
"reasons": {}
},
{
"tool": "send_draft",
"tags": [],
"reasons": {}
},
{
"tool": "get_identities",
"tags": [],
"reasons": {}
},
{
"tool": "list_mailboxes",
"tags": [],
"reasons": {}
},
{
"tool": "create_mailbox",
"tags": [],
"reasons": {}
},
{
"tool": "rename_mailbox",
"tags": [],
"reasons": {}
},
{
"tool": "delete_mailbox",
"tags": [],
"reasons": {}
},
{
"tool": "summarize_email",
"tags": [],
"reasons": {}
},
{
"tool": "suggest_reply",
"tags": [],
"reasons": {}
}
],
"surfaceDigest": "cd188915ac510969944b54d071ffcf667dd534070433dc8b133904f814e27bf4",
"stats": {
"tools": 47,
"prompts": 0,
"resources": 0,
"findingsBySeverity": {
"critical": 0,
"high": 0,
"medium": 1,
"low": 0,
"info": 0
}
}
}