Check whether a secret key exists in the vault.
AI agents call vault_exists to retrieve information from Secret Vault MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool only retrieves metadata about the existence of a secret key without accessing the secret's contents, modifying state, or triggering external operations. It is a safe, non-destructive information query with minimal blast radius if misused by an AI agent.
From the tool's definition Tool name 'vault_exists' and description 'Check whether a secret key exists in the vault' indicate a read-only query operation that returns a boolean result without modifying, executing, or deleting any data.
Attacks that exploit this kind of access
Check whether a secret key exists in the vault. It is categorised as a Read tool in the Secret Vault MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Secret Vault MCP Server MCP server in PolicyLayer and add a rule for vault_exists: 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 Secret Vault MCP Server. Nothing to install.
vault_exists is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the vault_exists 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 vault_exists. 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.
vault_exists is provided by the Secret Vault MCP Server MCP server (sam-ueckert/vault-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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