Create or replace a Vault policy with the given name and HCL policy string.
AI agents use create_policy to create or update resources in HashiCorp Vault MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your HashiCorp Vault MCP Server environment.
This tool creates or modifies Vault ACL policies, which are critical security configurations that control access to secrets and infrastructure. While reversible (policies can be updated again), misuse by an AI agent could grant unauthorized access to secrets or weaken security posture.
From the tool's definition Tool name 'create_policy' and description 'Create or replace a Vault policy' explicitly indicate creation and modification of access control policies. The phrase 'or replace' shows reversible mutation of policy data.
Documented attack patterns abuse exactly the kind of access create_policy gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and HashiCorp Vault MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for create_policy:
{
"version": "1",
"default": "deny",
"tools": {
"create_policy": {
"limits": [
{
"counter": "create_policy_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}create_policy 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.
Free to start. No card required.
Create or replace a Vault policy with the given name and HCL policy string. It is categorised as a Write tool in the HashiCorp Vault MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the HashiCorp Vault MCP Server MCP server in PolicyLayer and add a rule for create_policy: 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 HashiCorp Vault MCP Server. Nothing to install.
create_policy 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 create_policy 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 create_policy. 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.
create_policy is provided by the HashiCorp Vault MCP Server MCP server (rccyx/vault-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from HashiCorp Vault MCP Server, 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.
4 HashiCorp Vault MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.