patchEntityWithId
Updates, via PATCH, the Entity with the given Id.
This record as markdown: /tools/io-fusionauth-mcp-api/patchentitywithid.md
What patchEntityWithId does on Fusionauth
AI agents use patchEntityWithId to create or update resources in Fusionauth, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Fusionauth environment.
Why patchEntityWithId is rated Medium
This tool creates or modifies data reversibly through a PATCH operation on an entity identified by ID. It does not delete data (ruling out Destructive) nor execute arbitrary code (ruling out Execute).
From the tool's definition Tool description states it "Updates, via PATCH, the Entity with the given Id." PATCH is an HTTP method for partial modifications of resources, which aligns with reversible data modification.
Attacks that exploit this kind of access
The rule that runs patchEntityWithId safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Fusionauth, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For patchEntityWithId, this is the rule to start with:
patchEntityWithId 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 Fusionauth, apply this rule, and every patchEntityWithId call is checked against it from then on.
Questions about patchEntityWithId
Updates, via PATCH, the Entity with the given Id. It is categorised as a Write tool in the Fusionauth MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Fusionauth MCP server in PolicyLayer and add a rule for patchEntityWithId: 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 Fusionauth. Nothing to install.
patchEntityWithId 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 patchEntityWithId 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 patchEntityWithId. 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.
patchEntityWithId is provided by the Fusionauth MCP server (@fusionauth/mcp-api). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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