update_call

THE RISK

Medium Risk

Why update_call needs a policy

This tool modifies call state/status in an AP2 payment system context. While it affects communication records, the operation is reversible (status can be updated again) rather than destructive. It does not execute arbitrary operations, delete data, or move funds.

From the tool's definition Tool name 'update_call' with description 'Modify an in-progress call' indicates a reversible modification operation. The incomplete description 'Set Status=' suggests state changes to call records.

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

POLICY

How to control update_call

PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Ap2, and nothing reaches the server without passing your rules. This is the rule we recommend for update_call:

policy.json

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

update_call 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 Ap2 — 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 →

Free to start. No card required.

EXPLORE

Related tools and policies

More Mcp Ap2 tools

Financial authorize_transaction Authorize a transaction (reserve funds without capturing) via Braintree GraphQL authorizeP Financial block_card Block a card temporarily (reversible). Use for lost-card or fraud-suspected flows. Card st Financial cancel_bill Cancel a pending bill Financial cancel_collection Cancel a scheduled collection request Financial cancel_credit Cancel an authorized-but-uncaptured credit payment. Financial cancel_debit Cancel a debit-card payment by Getnet payment_id. Financial cancel_invoice Cancel/void an authorized invoice (FECancel — limited to certain types/conditions) Financial cancel_order Cancel an order, optionally restocking and refunding

All 1300 Mcp Ap2 tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

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_call

What does the update_call tool do? +

Modify an in-progress call. Set Status=. It is categorised as a Write tool in the Mcp Ap2 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_call? +

Register the Mcp Ap2 MCP server in PolicyLayer and add a rule for update_call: 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 Ap2. Nothing to install.

What risk level is update_call? +

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

Can I rate-limit update_call? +

Yes. Add a rate_limit block to the update_call 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_call completely? +

Set action: deny in the PolicyLayer policy for update_call. 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_call? +

update_call is provided by the Mcp Ap2 MCP server (@codespar/mcp-ap2). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Mcp Ap2 tool call.

Start from Mcp Ap2, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →