Billy — 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": "billy-mcp",
"source": {
"kind": "package",
"origin": "billy-mcp"
},
"server": {
"name": "billy-mcp"
}
},
"grade": "A",
"score": {
"score": 93,
"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": "high",
"label": "capability blast radius (high) — client exposure if the model is manipulated",
"appliedPenalty": 6
},
{
"kind": "client",
"term": "verification-discount",
"level": "repo",
"label": "publisher verification (public source) — no provenance, but the source is public and inspectable",
"appliedPenalty": 1
},
{
"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": "high",
"reasons": [
"can send data / act on an external service",
"reads sensitive or local data",
"has a read → egress path (a data-exfiltration surface)",
"can execute shell commands or code"
],
"tags": [
"sensitive-source",
"external-sink",
"code-exec"
]
},
"coverage": {
"level": "source",
"inputs": {
"toolSurface": true,
"implementationSource": true,
"packageMetadata": true,
"liveTransport": false
},
"caveats": [
"Tools were statically extracted from the published source (40 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-003",
"title": "Read-and-egress in one tool: \"attach_file\"",
"category": "exfiltration",
"severity": "high",
"confidence": "strong",
"description": "Tool \"attach_file\" can both read sensitive data and send data to an external destination. Even without an explicit untrusted-input leg, this is a single-call data-exfiltration path if the model is ever manipulated.",
"remediation": "Separate reading from sending; require explicit user confirmation before egress of file/secret contents.",
"location": {
"kind": "flow",
"name": "attach_file"
},
"owasp": "LLM02:2025 Sensitive Information Disclosure",
"references": [],
"data": {
"tags": [
"sensitive-source",
"external-sink"
]
}
},
{
"ruleId": "MTC-FLOW-004",
"title": "Sensitive-source and external-sink co-exist",
"category": "exfiltration",
"severity": "high",
"confidence": "strong",
"description": "Tools that read sensitive data ([list_files, attach_file]) and tools that can send data out ([upload_file, attach_file, execute_script]) are exposed together. An agent can move private data to the sink.",
"remediation": "Keep secret-reading and egress capabilities on separate, separately-approved servers.",
"location": {
"kind": "flow",
"name": "list_files → upload_file"
},
"evidence": "sources [list_files, attach_file] → sinks [upload_file, attach_file, execute_script]",
"owasp": "LLM02:2025 Sensitive Information Disclosure",
"references": [],
"data": {
"sources": [
"list_files",
"attach_file"
],
"sinks": [
"upload_file",
"attach_file",
"execute_script"
]
}
},
{
"ruleId": "MTC-CAP-001",
"title": "Tool \"execute_script\" exposes command/code execution",
"category": "permissions",
"severity": "high",
"confidence": "strong",
"description": "Tool \"execute_script\" appears to run shell commands or evaluate code (parameter \"script\"). Arbitrary execution driven by model input is one of the most dangerous MCP capabilities; combined with any untrusted input it becomes RCE.",
"remediation": "Sandbox execution, allowlist commands/arguments, and never pass model output to a shell unescaped.",
"location": {
"kind": "tool",
"name": "execute_script"
},
"owasp": "LLM05:2025 Improper Output Handling",
"data": {
"tags": [
"code-exec"
]
}
},
{
"ruleId": "MTC-CAP-006",
"title": "Unconstrained command parameter \"script\" on \"execute_script\"",
"category": "permissions",
"severity": "medium",
"confidence": "heuristic",
"description": "Tool \"execute_script\" takes a command-shaped parameter \"script\" with no enum/pattern constraint. Free-form, model- or attacker-controlled arguments reaching a shell is the command-injection precondition.",
"remediation": "Constrain the parameter (enum/pattern), or build the command from a fixed template with escaped args.",
"location": {
"kind": "tool",
"name": "execute_script",
"field": "inputSchema.properties.script"
},
"owasp": "LLM05:2025 Improper Output Handling",
"data": {
"param": "script"
}
},
{
"ruleId": "MTC-CAP-005",
"title": "Mutating tool \"execute_script\" declares no destructiveHint",
"category": "hygiene",
"severity": "low",
"confidence": "heuristic",
"description": "Tool \"execute_script\" can mutate/egress but declares no destructiveHint. Clients that don't default to spec-safe behavior may not prompt before running it.",
"remediation": "Declare accurate annotations, and gate destructive tools on user confirmation regardless.",
"location": {
"kind": "tool",
"name": "execute_script"
},
"data": {
"tags": [
"code-exec"
]
}
}
],
"toxicFlows": [
{
"id": "flow-1",
"severity": "high",
"confidence": "strong",
"untrustedInput": [],
"sensitiveSource": [
"attach_file"
],
"externalSink": [
"attach_file"
],
"selfContained": true,
"description": "Tool \"attach_file\" both reads sensitive data and can send it externally."
},
{
"id": "flow-2",
"severity": "high",
"confidence": "strong",
"untrustedInput": [],
"sensitiveSource": [
"list_files",
"attach_file"
],
"externalSink": [
"upload_file",
"attach_file",
"execute_script"
],
"selfContained": false,
"path": [
"attach_file",
"execute_script"
],
"pathWired": false,
"description": "A sensitive-source → external-sink chain exists: attach_file → execute_script."
}
],
"capabilities": [
{
"tool": "list_accounts",
"tags": [],
"reasons": {}
},
{
"tool": "get_account",
"tags": [],
"reasons": {}
},
{
"tool": "list_daybook_transactions",
"tags": [],
"reasons": {}
},
{
"tool": "list_files",
"tags": [
"sensitive-source"
],
"reasons": {
"sensitive-source": [
"keyword \"list_files\""
]
}
},
{
"tool": "list_attachments",
"tags": [],
"reasons": {}
},
{
"tool": "upload_file",
"tags": [
"external-sink"
],
"reasons": {
"external-sink": [
"keyword \"upload_file\""
]
}
},
{
"tool": "attach_file",
"tags": [
"sensitive-source",
"external-sink"
],
"reasons": {
"sensitive-source": [
"keyword \"list_files\""
],
"external-sink": [
"keyword \"upload_file\""
]
}
},
{
"tool": "list_bills",
"tags": [],
"reasons": {}
},
{
"tool": "get_bill",
"tags": [],
"reasons": {}
},
{
"tool": "create_bill",
"tags": [],
"reasons": {}
},
{
"tool": "list_contacts",
"tags": [],
"reasons": {}
},
{
"tool": "get_contact",
"tags": [],
"reasons": {}
},
{
"tool": "create_contact",
"tags": [],
"reasons": {}
},
{
"tool": "update_contact",
"tags": [],
"reasons": {}
},
{
"tool": "list_contact_persons",
"tags": [],
"reasons": {}
},
{
"tool": "create_contact_person",
"tags": [],
"reasons": {}
},
{
"tool": "list_daybooks",
"tags": [],
"reasons": {}
},
{
"tool": "create_daybook_transaction",
"tags": [],
"reasons": {}
},
{
"tool": "void_daybook_transaction",
"tags": [],
"reasons": {}
},
{
"tool": "batch_void_daybook_transactions",
"tags": [],
"reasons": {}
},
{
"tool": "list_invoices",
"tags": [],
"reasons": {}
},
{
"tool": "get_invoice",
"tags": [],
"reasons": {}
},
{
"tool": "create_invoice",
"tags": [],
"reasons": {}
},
{
"tool": "approve_invoice",
"tags": [],
"reasons": {}
},
{
"tool": "delete_invoice",
"tags": [],
"reasons": {}
},
{
"tool": "billy_raw_request",
"tags": [],
"reasons": {}
},
{
"tool": "get_organization",
"tags": [],
"reasons": {}
},
{
"tool": "create_bank_payment",
"tags": [],
"reasons": {}
},
{
"tool": "list_bank_payments",
"tags": [],
"reasons": {}
},
{
"tool": "list_balance_modifiers",
"tags": [],
"reasons": {}
},
{
"tool": "list_products",
"tags": [],
"reasons": {}
},
{
"tool": "get_product",
"tags": [],
"reasons": {}
},
{
"tool": "create_product",
"tags": [],
"reasons": {}
},
{
"tool": "update_product",
"tags": [],
"reasons": {}
},
{
"tool": "get_account_balances",
"tags": [],
"reasons": {}
},
{
"tool": "list_postings",
"tags": [],
"reasons": {}
},
{
"tool": "list_transactions",
"tags": [],
"reasons": {}
},
{
"tool": "list_bank_lines",
"tags": [],
"reasons": {}
},
{
"tool": "list_bank_line_matches",
"tags": [],
"reasons": {}
},
{
"tool": "execute_script",
"tags": [
"code-exec"
],
"reasons": {
"code-exec": [
"parameter \"script\""
]
}
}
],
"surfaceDigest": "7f6b3f5a84c902e4270684797d1ce4fd1108701ec58ceb63c892c30b014468ba",
"stats": {
"tools": 40,
"prompts": 0,
"resources": 0,
"findingsBySeverity": {
"critical": 0,
"high": 3,
"medium": 1,
"low": 1,
"info": 0
}
}
}