v0 MCP tool approval and Sume: ask first before paid calls
v0 lets you disable tools and set ask-for-approval or auto-use per MCP. Pair that with Sume's dry_run and max_spend_usd so a paid call never runs unreviewed.
Set Sume's tools to ask-for-approval in v0, switch off any tool you do not need, and have the agent send dry_run=true and max_spend_usd on paid calls. v0's MCP docs say you can enable or disable individual tools and choose between ask-for-approval and auto-use in permission settings. Sume's own gates sit behind that prompt; neither one replaces the other.
Sources, read 2026-10-06: v0's MCP docs, Sume's MCP tools and gates and Safe automation.
Which Sume gates pair with an approval prompt?
The table below lists each item as documented.
| Layer | Control | What it does |
|---|---|---|
| v0 | Disable a tool | The agent cannot call it at all |
| v0 | Ask for approval | You see the call before it runs |
| Sume | dry_run=true | Previews without submitting |
| Sume | max_spend_usd | Caps spend only when the call sends it |
| Sume | idempotency_key | Required on writes and paid calls; makes a retry safe |
What should the approval prompt show?
Read the arguments before approving. A paid create without max_spend_usd has no per-call cap, because Sume enforces it only when sent. A create without idempotency_key is rejected, which is a safe failure. If an approved call times out in v0, do not approve a second create: wait on the job id with jobs_wait instead.
Auto-use is a decision, not a default
Auto-use fits read-only tools such as tools_list, tools_schema and mcp_health. For paid tools, leave approval on, or give the agent an OAuth grant without mcp:write so write tools are not available to it.
Sources
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