Update an existing plan. Endpoint: PUT /plans/:id
AI agents use update_plan to create or update resources in Mcp Ap2 — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Mcp Ap2 environment.
This tool modifies plan data reversibly via PUT request. It is not destructive (does not delete), not directly financial (does not move money itself, though it affects payment plans), and not Execute (does not run arbitrary code).
From the tool's definition Tool name 'update_plan' with description 'Update an existing plan' and PUT endpoint indicates modification of existing plan data. Server context is AP2 (Google's Agent-to-Agent Payment Protocol), making this financial infrastructure.
Documented attack patterns abuse exactly the kind of access update_plan gives an agent:
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_plan:
{
"version": "1",
"default": "deny",
"tools": {
"update_plan": {
"limits": [
{
"counter": "update_plan_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update_plan 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.
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Update an existing plan. Endpoint: PUT /plans/:id. 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.
Register the Mcp Ap2 MCP server in PolicyLayer and add a rule for update_plan: 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.
update_plan is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the update_plan 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.
Set action: deny in the PolicyLayer policy for update_plan. 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.
update_plan 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.
Start from Mcp Ap2, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
1300 Mcp Ap2 tools catalogued and risk-classified — across an index of 43,000+ MCP servers.