Build a gateway that exposes any-size tool registry through just two
meta-tools: search(query) and execute(tool_name, **params). Tool
descriptions stay outside the prompt entirely — the agent's prompt
cost is constant regardless of registry size. Use when you need
per-tenant tool segmentation, per-agent access policies, or are
scaling to hundreds-of-tools where even top-k injection (rag-mcp-
tool-selection) bloats prompts. NOT for cases under 30 tools where
RAG-MCP top-K injection is simpler. NOT a security layer on its own
— bring an IAM/RBAC source-of-truth for the access_filter.
