Insert a hierarchical-sheet reference block into a parent schematic, pointing at an existing sub-sheet file. Adds the sheet box, name/file fields, a sheet_instances path entry on the next page number, and fixes sub-sheet component instance paths so ERC resolves references.
AI agents use add_hierarchical_sheet to create or update resources in KiCAD-MCP-Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your KiCAD-MCP-Server environment.
The tool creates and modifies schematic structure by inserting hierarchical sheet references and updating internal references. While it changes the design, these modifications are reversible (sheets can be removed, references can be re-corrected). It does not execute code, delete irreversibly, or move money.
From the tool's definition Tool performs 'Insert', 'Adds', and 'fixes' operations on schematic data - creating new sheet reference blocks and modifying sheet_instances and component paths. These are reversible modifications to design files.
Documented attack patterns abuse exactly the kind of access add_hierarchical_sheet gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and KiCAD-MCP-Server, and nothing reaches the server without passing your rules. This is the rule we recommend for add_hierarchical_sheet:
{
"version": "1",
"default": "deny",
"tools": {
"add_hierarchical_sheet": {
"limits": [
{
"counter": "add_hierarchical_sheet_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
} add_hierarchical_sheet stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
Free to start. No card required.
Insert a hierarchical-sheet reference block into a parent schematic, pointing at an existing sub-sheet file. Adds the sheet box, name/file fields, a sheet_instances path entry on the next page number, and fixes sub-sheet component instance paths so ERC resolves references. It is categorised as a Write tool in the KiCAD-MCP-Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the KiCAD-MCP-Server MCP server in PolicyLayer and add a rule for add_hierarchical_sheet: 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 KiCAD-MCP-Server. Nothing to install.
add_hierarchical_sheet 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 add_hierarchical_sheet 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 add_hierarchical_sheet. 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.
add_hierarchical_sheet is provided by the KiCAD-MCP-Server MCP server (mixelpixx/kicad-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from KiCAD-MCP-Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
157 KiCAD-MCP-Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.