UC-016: Hidden/Extra Args in Tool Call

Layer: B — Dispatch Enforcement Threat: Tool Misuse / Parameter Injection

Scenario

A tool call includes valid declared arguments plus additional undeclared fields that could influence downstream behavior.

Expected Behavior

• Extra fields in tool call args → DENY
• Deny-on-unknown-fields enforced at schema PEP
• Signed deny receipt produced

Pass Criteria

• Verdict: DENY
• Extra fields rejected, not silently ignored
• Receipt: signed with full ArgsHash