replace_instance_lib_ids
Replace lib_id references in schematic symbol instances per an explicit old-to-new mapping — the mechanical layer of a library migration (e.g. eagle_import symbols to curated library symbols). Mirror-variant suffixes (__m0/__m90/__m180/__m270) get automatic angle correction; each needs its own ma...
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What replace_instance_lib_ids does on KiCAD-MCP-Server
AI agents use replace_instance_lib_ids 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.
Why replace_instance_lib_ids is rated Medium
This tool modifies symbol instance references in a KiCAD schematic, which is a reversible alteration of design data. The operation changes which library symbols are referenced without deleting the underlying symbol definitions (those are preserved per the description).
From the tool's definition Tool description states it "Replace[s] lib_id references in schematic symbol instances" and "instances are rewritten", indicating modification of existing symbol data in the schematic.
Attacks that exploit this kind of access
The rule that runs replace_instance_lib_ids safely
PolicyLayer is an MCP gateway: it sits between your AI agents and KiCAD-MCP-Server, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For replace_instance_lib_ids, this is the rule to start with:
replace_instance_lib_ids 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.
The button opens the PolicyLayer dashboard: create your workspace, connect KiCAD-MCP-Server, apply this rule, and every replace_instance_lib_ids call is checked against it from then on.
Questions about replace_instance_lib_ids
Replace lib_id references in schematic symbol instances per an explicit old-to-new mapping — the mechanical layer of a library migration (e.g. eagle_import symbols to curated library symbols). Mirror-variant suffixes (__m0/__m90/__m180/__m270) get automatic angle correction; each needs its own mapping entry. Only instances are rewritten; lib_symbols is preserved (use update_symbol_from_library to refresh definitions afterwards). 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 replace_instance_lib_ids: 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.
replace_instance_lib_ids 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 replace_instance_lib_ids 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 replace_instance_lib_ids. 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.
replace_instance_lib_ids 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.
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