Group data by columns and perform aggregation (like Excel Pivot Table). Returns grouped results with aggregated values. Supports multiple grouping columns for hierarchical analysis. Use for: pivot tables, data summarization, category analysis, hierarchical grouping, sales by region/product, perfo...
AI agents call group_by to retrieve information from Mcp Excel without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
group_by is a pure read operation that retrieves, groups, and aggregates existing data without modifying, deleting, or executing arbitrary code. It performs the same function as Excel's Pivot Table feature—summarizing data through grouping and aggregation. There are no side effects, data modification, deletion, or financial implications.
From the tool's definition The tool description explicitly states it 'Group data by columns and perform aggregation' and returns 'grouped results with aggregated values'.
Documented attack patterns abuse exactly the kind of access group_by gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Excel, and nothing reaches the server without passing your rules. This is the rule we recommend for group_by:
{
"version": "1",
"default": "deny",
"tools": {
"group_by": {}
}
}group_by is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Group data by columns and perform aggregation (like Excel Pivot Table). Returns grouped results with aggregated values. Supports multiple grouping columns for hierarchical analysis. Use for: pivot tables, data summarization, category analysis, hierarchical grouping, sales by region/product, performance by team/month. EXAMPLES: Revenue by product category, Average salary by department and job level, Count of orders by customer and month. It is categorised as a Read tool in the Mcp Excel MCP Server, which means it retrieves data without modifying state.
Register the Mcp Excel MCP server in PolicyLayer and add a rule for group_by: 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 Mcp Excel. Nothing to install.
group_by 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 group_by 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 group_by. 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.
group_by is provided by the Mcp Excel MCP server (jwadow/mcp-excel). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Mcp Excel, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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25 Mcp Excel tools catalogued and risk-classified — across an index of 43,000+ MCP servers.