rhino_block_redefine
Replace a block definition's geometry, propagating to every instance (bridge only).
This record as markdown: /tools/easehee-rhino-mcp/rhino-block-redefine.md
What rhino_block_redefine does on Rhino
AI agents use rhino_block_redefine to create or update resources in Rhino, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Rhino environment.
Why rhino_block_redefine is rated Medium
The tool modifies geometry data (blocks) within a Rhino document that are used across multiple instances. This is a reversible write operation (can be undone/redefined again), not destructive deletion. However, it has high severity due to the blast radius: redefining a block affects every instance in the project simultaneously, which could substantially alter a design or model.
From the tool's definition Tool description states 'Replace a block definition's geometry, propagating to every instance' — this modifies existing block definitions in Rhino, affecting all instances of that block across the model.
Risk signalsBulk/mass operation — affects multiple targets
Attacks that exploit this kind of access
The rule that runs rhino_block_redefine safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Rhino, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For rhino_block_redefine, this is the rule to start with:
rhino_block_redefine 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 Rhino, apply this rule, and every rhino_block_redefine call is checked against it from then on.
Questions about rhino_block_redefine
Replace a block definition's geometry, propagating to every instance (bridge only). It is categorised as a Write tool in the Rhino MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Rhino MCP server in PolicyLayer and add a rule for rhino_block_redefine: 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 Rhino. Nothing to install.
rhino_block_redefine 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 rhino_block_redefine 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 rhino_block_redefine. 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.
rhino_block_redefine is provided by the Rhino MCP server (easehee/rhino-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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