MCP tool call authorization
MCP gives agents tools. Permission Protocol gives those tools authority boundaries.
As agents gain MCP tools, static permission lists are not enough. Sensitive tool calls need explicit authorization at the moment of action.
The problem
An agent with a broad MCP tool can delete data, modify infrastructure, message customers, or move money with the same interface it uses for harmless reads.
Tool allowlists describe capability. They do not prove a specific high-risk call was authorized.
Self-policing agents can rationalize risky calls when success metrics reward task completion over governance.
How Permission Protocol handles it
Wrap sensitive MCP tools with an authorization request before execution.
Route approval to the right human based on action type, environment, amount, or blast radius.
Fail closed when no valid receipt exists.
Concrete bad scenario
An agent has an MCP tool that can update Stripe, delete rows, or message customers. The same server also exposes harmless read-only methods, so a broad allowlist cannot distinguish inspection from production mutation.
Policy Permission Protocol applies
Read-only calls auto-clear. Mutations over customer data require approval. Refunds above $500 require a finance signer. Broadcast customer messages require a support or growth owner. Destructive data deletion is denied unless routed through an approved break-glass policy.
Exact enforcement point
The MCP server or tool wrapper calls Permission Protocol before executing high-risk methods. If no valid receipt exists for the exact tool, method, resource, amount, and actor, the call fails closed.
Sample receipt
Would Permission Protocol block this?
Stripe refund over $500
The agent requests a $1,200 refund. The tool pauses until a finance signer approves the exact customer, amount, and reason.
Customer record read
The agent reads a customer status field. Policy treats it as low-risk and clears the call without human interruption.
Bulk row deletion
The agent requests a broad delete over customer data. Policy denies the call unless it enters a separate break-glass workflow.
Implementation checklist
- 1Identify tools that mutate production, customer data, payments, messaging, or infrastructure.
- 2Wrap those calls with Permission Protocol before execution.
- 3Set policies for auto-clear, approval_required, and denied outcomes.
- 4Store receipts with the action logs so audits can prove authorization.
FAQ
Is an MCP allowlist enough?
Not for high-risk tools. An allowlist says the agent can call a tool. Permission Protocol proves this exact call was authorized before it executed.
Does this slow every tool call down?
No. Only sensitive calls need a gate. Read-only and low-risk actions can clear automatically under policy.
What if Permission Protocol is unreachable?
Sensitive actions should fail closed. No receipt means no execution.