# HARN-CAP-007 — tool host capability binding is invalid
**Category:** Host capability (CAP)
**Variant:** `Code::CapabilityBindingInvalid` (capability binding invalid)
## What it means
A host capability call (file I/O, network, HITL approval, tool host, etc.) is
shaped in a way Harn cannot statically validate. Capabilities are the trust
boundary between Harn scripts and the embedding host, so the check is strict by
design.
Specifically: tool host capability binding is invalid.
## How to fix
- Match the capability signature documented in the Harn capability spec.
- If approval / receipt handling is required, wire it through `human_approval` or the equivalent before calling the capability.
## Stability
This code is stable. Its identifier, category, and meaning will not change
without a deprecation cycle. Cross-language tooling and IDE integrations can
dispatch on it directly.