Response Redaction

AxonFlow automatically detects and redacts sensitive data in MCP connector responses before they reach your application. This provides a security layer that protects PII and other sensitive information.

How Redaction Works

When a connector returns data, AxonFlow:

1. Scans Response Data: Recursively examines all fields in the response
2. Pattern Matching: Applies regex patterns to detect sensitive data
3. Validation: Runs validators (Luhn, checksum) to reduce false positives
4. Redaction: Replaces sensitive values with [REDACTED] placeholder
5. Metadata: Records which fields were redacted in redacted_fields

Redacted Response Example

Original data from connector:

{
  "customer_id": 12345,
  "name": "Jane Smith",
  "ssn": "123-45-6789",
  "credit_card": "4111-1111-1111-1111",
  "email": "[email protected]"
}

After redaction:

{
  "customer_id": 12345,
  "name": "Jane Smith",
  "ssn": "[REDACTED]",
  "credit_card": "[REDACTED]",
  "email": "[email protected]"
}

Response metadata:

{
  "redacted": true,
  "redacted_fields": [
    "data[0].ssn",
    "data[0].credit_card"
  ],
  "policy_info": {
    "redactions_applied": 2,
    "matched_policies": [
      {"policy_id": "pii-us-ssn", "policy_name": "US Social Security Number", "category": "pii-us", "severity": "critical", "action": "redact"},
      {"policy_id": "pii-global-credit-card", "policy_name": "Global Credit Card", "category": "pii-global", "severity": "critical", "action": "redact"}
    ]
  }
}

PII Categories

Global PII

Type	Pattern	Validator
Credit Card	13-19 digits	Luhn algorithm
Email	RFC 5322 pattern	Format check
Phone	International formats	Format check
IP Address	IPv4/IPv6	Format check

US PII

Type	Pattern	Validator
SSN	XXX-XX-XXXX	Area/group rules
Driver's License	State-specific	Format check
Passport	9 alphanumeric	Format check
Bank Routing	9 digits	ABA checksum

India PII

Type	Pattern	Validator
Aadhaar	12 digits	Verhoeff checksum
PAN	XXXXX0000X	Entity type check
Passport	X0000000	Format check

EU PII

Type	Pattern	Validator
IBAN	Country-specific	MOD97 checksum
National ID	Country-specific	Format check
VAT Number	Country prefix	Format check

Redaction Strategies

Full Redaction (Default)

Replaces the entire value:

123-45-6789 → [REDACTED]

Partial Redaction

Preserves part of the value for reference:

123-45-6789 → XXX-XX-6789
4111-1111-1111-1111 → XXXX-XXXX-XXXX-1111

Configure with REDACTION_STRATEGY=partial.

Hash Redaction

Replaces with a consistent hash for deduplication:

123-45-6789 → [HASH:a1b2c3d4]

Configure with REDACTION_STRATEGY=hash.

SDK Handling

Check for redacted fields in your application:

// Go
resp, _ := client.MCPQuery(ctx, req)

if resp.Redacted {
    // Log redaction for audit
    log.Printf("Data redacted: %v", resp.RedactedFields)

    // Check if critical fields were redacted
    for _, field := range resp.RedactedFields {
        if strings.Contains(field, "required_field") {
            return errors.New("required field was redacted")
        }
    }
}

// TypeScript
const resp = await client.mcpQuery(req);

if (resp.redacted) {
  // Handle redacted data
  console.warn("Some fields were redacted:", resp.redacted_fields);

  // Optionally notify user
  if (resp.redacted_fields?.some(f => f.includes("payment"))) {
    showMessage("Payment details are protected");
  }
}

Selective Redaction

Configure which categories to redact per tenant:

-- Only redact critical PII (SSN, credit cards)
INSERT INTO static_policies (tenant_id, category, severity, action_response)
VALUES ('tenant-1', 'pii-us', 'critical', 'redact');

-- Log but don't redact medium severity
INSERT INTO static_policies (tenant_id, category, severity, action_response)
VALUES ('tenant-1', 'pii-global', 'medium', 'log');

Bypassing Redaction

For authorized use cases, request unredacted data:

{
  "connector": "postgres-demo",
  "statement": "SELECT * FROM customers",
  "options": {
    "bypass_redaction": true,
    "justification": "Customer support case #12345"
  }
}

Requires pii.bypass permission and logs to audit trail.

Performance

Redaction is optimized for minimal latency:

• Streaming Processing: Data processed as it's received
• Compiled Patterns: Regex patterns pre-compiled at startup
• Parallel Scanning: Multiple fields scanned concurrently
• Early Exit: Stops scanning when max redactions reached

Typical performance:

• 100 fields: <2ms
• 1000 fields: <10ms
• 10000 fields: <50ms

Audit Trail

All redactions are logged for compliance:

{
  "event": "pii_redacted",
  "timestamp": "2026-01-09T12:00:00Z",
  "tenant_id": "tenant-1",
  "connector": "postgres-demo",
  "user_id": "user-123",
  "fields_redacted": ["ssn", "credit_card"],
  "policies_matched": ["pii-us-ssn", "pii-global-credit-card"]
}

Troubleshooting

False Positives

If legitimate data is being redacted:

1. Check the matched_policies in response
2. Review pattern configuration for that policy
3. Add exclusion pattern if needed:

UPDATE static_policies
SET exclude_pattern = 'test|sample|demo'
WHERE id = 'problematic-policy-id';

Missing Redactions

If sensitive data isn't being redacted:

1. Verify policy is enabled: enabled = true
2. Check phase: phase IN ('response', 'both')
3. Check severity threshold: severity >= 'medium'
4. Verify pattern matches your data format

Related Documentation

• MCP Policy Enforcement
• PII Detection
• Audit Logging