Update fields on an existing applicant. Send only the fields you want to change.
AI agents use update_applicant 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 applicant records reversibly (updates, not deletions). While it operates within a payment/financial protocol context (AP2 - Agent-to-Agent Payment Protocol), the tool itself performs data modification rather than moving money or creating financial obligations.
From the tool's definition Tool name 'update_applicant' combined with description 'Update fields on an existing applicant' indicates modification of existing data records.
Documented attack patterns abuse exactly the kind of access update_applicant 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_applicant:
{
"version": "1",
"default": "deny",
"tools": {
"update_applicant": {
"limits": [
{
"counter": "update_applicant_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update_applicant 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 fields on an existing applicant. Send only the fields you want to change. 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_applicant: 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_applicant 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_applicant 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_applicant. 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_applicant 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.
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1300 Mcp Ap2 tools catalogued and risk-classified — across an index of 43,000+ MCP servers.