AI agents call list_clients 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 returns client data without creating, modifying, or deleting anything. It is a straightforward read operation typical of list/search functionality. The optional filtering parameter allows refined queries but does not change the nature of the operation as read-only.
From the tool's definition Tool name 'list_clients' and description 'List clients with optional filtering' indicate a retrieval operation with no modification or side effects.
Documented attack patterns abuse exactly the kind of access list_clients 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_clients:
{
"version": "1",
"default": "deny",
"tools": {
"list_clients": {}
}
}list_clients is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List clients with optional filtering. 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_clients: 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_clients 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_clients 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_clients. 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_clients 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.