Tool
A governed capability with a fixed schema, a risk level and an execution policy.
A tool is a logical capability — sample.echo, billing.refund — that groups the versions implementing it. A version pins a reviewed specification: input and output schemas, required permissions, risk level, timeouts, retry and idempotency policy. Versions are immutable; changing one means publishing a new version.
Bindings
A binding pins exactly one published version into one environment, over either the safe simulator or a fixed HTTPS origin and path. Transport, route and secret reference are trusted binding fields — they are set by you and are never model input.
The playground
Validation checks arguments against the published schema and reports the risk level, action category and confirmation mode. It never touches tenant data or credentials, and it never calls the host.