# MAS-06 Per-hop invocation logging

Domain: MAS Multi-Agent Systems · HI-AAF v1.3 · Public review · https://humanintel.net/standard/mas/mas-06

Each agent-to-agent invocation is logged under MON-01, including caller identity, callee identity, purpose, input, output, and a chain identifier linking the hop to its originating user request.

Each agent-to-agent invocation is logged under MON-01, including caller identity, callee identity, purpose, input, output, and a chain identifier linking the hop to its originating user request. Logs are sufficient to reconstruct the full chain after the fact. This control is the multi-agent extension of MON-01 and is essential for incident investigation in complex agent topologies.

## Maturity

- L1 Ad hoc: Controls exist informally; documentation is incomplete; no consistent review.
- L2 Documented: Controls are written down; ownership is assigned; review cadence is defined.
- L3 Operated: Controls are followed in practice; evidence is collected; deviations are tracked. Published criterion for MAS-06: Per-hop logging is active for all agent-to-agent invocations; chain identifiers are present and sufficient to reconstruct the full chain; log completeness has been verified through sampling.
- L4 Measured: Control effectiveness is measured against documented thresholds; trends are reported.
- L5 Continuously Improved: Controls evolve based on incident learning; maturity gains are evidenced over time.

## Evidence an assessor asks for

- Per-hop logging is active for all agent-to-agent invocations.
- Chain identifiers are present and sufficient to reconstruct the full chain.
- Log completeness has been verified through sampling.

## Framework mappings

- NIST AI RMF: MANAGE 4.1
- SOC 2 (TSC): CC7.2, CC7.3
- EU AI Act: Art. 14(4)
- Singapore: MAIGF Accountability

Mappings are directional: meeting this control evidences but does not by itself satisfy the external requirement.

## Related

- Cites MON-01 Per-step logging: https://humanintel.net/standard/mon/mon-01
- Cited by MON-01 Per-step logging: https://humanintel.net/standard/mon/mon-01
- Glossary: Agent-to-agent: https://humanintel.net/standard/glossary#agent-to-agent
- Glossary: Chain identifier: https://humanintel.net/standard/glossary#chain-identifier

## Cite this control

Human Intelligence. HI-AAF v1.3, MAS-06 Per-hop invocation logging. Public review edition, July 2026. https://humanintel.net/standard/mas/mas-06