AI agents call list_users to retrieve information from Harvest MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries and retrieves user data from the Harvest account without creating, modifying, deleting, or executing any operations. It is a straightforward read-only operation that returns user information. The blast radius is minimal as it only exposes existing user metadata without side effects.
From the tool's definition Tool name 'list_users' and description 'List all users in your Harvest account' indicate a retrieval operation with no modification or execution of external actions.
Risk signalsBulk/mass operation — affects multiple targets
Documented attack patterns abuse exactly the kind of access list_users gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Harvest MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list_users:
{
"version": "1",
"default": "deny",
"tools": {
"list_users": {}
}
}list_users is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List all users in your Harvest account. It is categorised as a Read tool in the Harvest MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Harvest MCP Server MCP server in PolicyLayer and add a rule for list_users: 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 Harvest MCP Server. Nothing to install.
list_users 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 list_users 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 list_users. 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.
list_users is provided by the Harvest MCP Server MCP server (taiste/harvest-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 21 Harvest MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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21 Harvest MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.