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Trust Score Explained

How MCPAmpel computes the 0-10 trust score from 16 scanning engines.

How the Trust Score Works

Every scan starts at a perfect 10.0. Each engine that flags findings deducts a penalty based on the worst severity it found, multiplied by the engine's weight. The final score is clamped to the 0.0-10.0 range.

The formula for each flagged engine: penalty = severity_weight * engine_weight, capped at 3.0 per engine. The total penalty is subtracted from 10.0 to produce the final score.

Score Ranges

8.0 - 10.0 Low risk. Few or no findings across engines. Safe to deploy with standard precautions.
5.0 - 7.9 Moderate risk. Multiple findings detected. Review flagged issues before deploying.
0.0 - 4.9 High risk. Significant findings from multiple engines. Immediate attention recommended.

Severity Penalties

Each flagged engine's worst finding determines the base penalty:

Severity Base Penalty
Critical3.0
High2.0
Medium1.0
Low0.3
Clean0.0

Engine Weights

Each engine has a weight that scales its penalty. Higher weight means more score impact.

Weight Engines
1.0 (Full) Trivy, Grype, OSV Scanner, Semgrep, Gitleaks, Custom YARA
0.7 (Good) Bandit, pip-audit
0.5 (Moderate) Cisco Skill, Cisco A2A, MCP Guardian
0.15 (Noisy) detect-secrets, Checkov
0.0 (Info) Syft, ScanCode, Cisco AIBOM

Informational engines (weight 0.0) produce findings but never reduce the trust score. They provide context like SBOMs and license data.

Worked Example

A repository scanned by all 16 engines. Three engines flag findings:

Semgrep (high, weight 1.0) 2.0 * 1.0 = 2.0
detect-secrets (low, weight 0.15) 0.3 * 0.15 = 0.045
Checkov (medium, weight 0.15) 1.0 * 0.15 = 0.15
Final score 10.0 - 2.195 = 7.8

The remaining 16 engines reported clean results, contributing no penalty. The score rounds to one decimal place.

What the Score Doesn't Cover

The trust score reflects what automated static analysis tools can detect. It does not cover:

- Runtime behavior and dynamic execution paths
- Zero-day vulnerabilities not yet in scanner databases
- Business logic flaws and application-level design issues
- Social engineering vectors and human-factor risks

A high score means the code passed automated checks, not that it is free of all security issues. Use the trust score as one signal alongside manual review and threat modeling.

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