One reserve_stock tool, one AIKUS-built server implementation in two explicitly selected versions, one local mock inventory, MCP protocol revision 2025-06-18 over stdio, sequential calls within a single process. Assumes the caller supplies a stable idempotency key; whether a given agent does is not tested.

Not tested: overlapping concurrent calls, lost responses, process crashes, key persistence across restart, expiration, multi-instance deployment, tenant isolation, authentication, shipping, cancellation, stale stock, recovery, retries after unsuccessful reservation responses or production. This implementation remembers a key only after a successful reservation. An unsuccessful response does not establish a remembered key, so a later retry can make a fresh attempt. That behaviour was not tested or established as an agreed error-handling policy. The fixed key map is in memory and this run does not establish durability. The remaining tools and three later lab tests have not been built or executed. No general MCP conformance claim is made.