update_amount

THE RISK

Medium Risk

Why update_amount needs a policy

This tool modifies existing payment authorizations (tips/hotel incidentals) but does not transfer funds, create new financial obligations, or delete data. It is a Write operation because it changes payment metadata reversibly. Severity is medium because misuse could modify payment amounts in ways that affect financial accuracy and customer trust, but the changes appear reversible through correction.

From the tool's definition Tool updates "authorized amount of an unsettled payment", which modifies financial data. The description explicitly references payments and adjustments to authorized amounts, indicating reversible modification of payment records rather than execution of…

Documented attack patterns abuse exactly the kind of access update_amount gives an agent:

POLICY

How to control update_amount

PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Afip, and nothing reaches the server without passing your rules. This is the rule we recommend for update_amount:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "update_amount": {
      "limits": [
        {
          "counter": "update_amount_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

update_amount stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register Mcp Afip — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

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EXPLORE

Related tools and policies

More Mcp Afip tools

Financial authorize_transaction Authorize a transaction (reserve funds without capturing) via Braintree GraphQL authorizeP Financial cancel_collection Cancel a scheduled collection request Financial cancel_credit Cancel an authorized-but-uncaptured credit payment. Financial cancel_payment Attempt to cancel a payment that has not yet settled. Iniciador endpoint: POST /payments/{ Financial cancel_payment_intent Cancel a payment intent that has not yet been captured. Fails on already-captured intents; Financial cancel_recurrence Cancel an active recurrence. Future charges will stop; already-charged cycles are untouche Financial cancel_subscription Cancel a subscription by ID Financial revoke_token Revoke an issued access_token or refresh_token at POST /v1/token/revoke. Use to terminate

All 1300 Mcp Afip tools →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about update_amount

What does the update_amount tool do? +

Update the authorized amount of an unsettled payment (common in tips / hotel incidentals). It is categorised as a Write tool in the Mcp Afip MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_amount? +

Register the Mcp Afip MCP server in PolicyLayer and add a rule for update_amount: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Mcp Afip. Nothing to install.

What risk level is update_amount? +

update_amount is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit update_amount? +

Yes. Add a rate_limit block to the update_amount rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block update_amount completely? +

Set action: deny in the PolicyLayer policy for update_amount. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides update_amount? +

update_amount is provided by the Mcp Afip MCP server (codespar/mcp-dev-latam). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Mcp Afip tool call.

Start from Mcp Afip, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →