Write a secret to a KV mount
Risk signalsStores sensitive credentials in Vault
Part of the HashiCorp Vault server.
Free to start. No card required.
AI agents use write_secret to create or modify resources in HashiCorp Vault. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.
Without a policy, an AI agent could call write_secret repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach HashiCorp Vault.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"write_secret": {
"limits": [
{
"counter": "write_secret_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full HashiCorp Vault policy for all 16 tools.
These attack patterns abuse exactly the kind of access write_secret gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Write a secret to a KV mount. It is categorised as a Write tool in the HashiCorp Vault MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the HashiCorp Vault MCP server in PolicyLayer and add a rule for write_secret: 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. Nothing to install.
write_secret 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 write_secret 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 write_secret. 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.
write_secret is provided by the HashiCorp Vault MCP server (@hashicorp/vault-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 16 HashiCorp Vault tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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