Optional fiscal-safety metadata for paid MCP servers

[egoriklok]

MCP server discovery is moving toward an app-store-like registry. As paid MCP servers and agent-accessible commercial tools appear, clients may need a small non-secret fiscal-safety layer before an agent is allowed to call a paid tool.

Possible optional metadata/checklist fields:

1. paid_action_surface — what action can create cost or settlement?
2. approval_source — human approval, policy engine, allowance, budget rule, or none.
3. spend_cap — per-call, per-session, daily, or monthly cap.
4. charge_evidence — what non-secret receipt/event proves a charge happened?
5. audit_trail — where a client/operator can verify calls and charges.
6. revocation_path — how access is disabled or reduced.
7. next_safe_threshold — what evidence would justify raising the cap.

The goal is not to collect secrets or payment credentials in the registry. It is to help agent clients distinguish a free/tooling MCP server from one that can trigger bounded paid actions, and to make revocation/audit expectations explicit.

Question for maintainers/builders: would this fit better as optional registry metadata, a convention in server docs, or a separate checklist linked from paid-server entries?