upsertEntityGrantWithId
Creates or updates an Entity Grant. This is when a User/Entity is granted permissions to an Entity.
This record as markdown: /tools/io-fusionauth-mcp-api/upsertentitygrantwithid.md
What upsertEntityGrantWithId does on Fusionauth
AI agents use upsertEntityGrantWithId 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 upsertEntityGrantWithId is rated Medium
The tool performs reversible Create/Update operations on entity permission grants. It does not delete or destroy data (ruling out Destructive), nor does it execute arbitrary code (ruling out Execute) or move money (ruling out Financial). The high severity reflects that granting/revoking permissions can broadly affect system access and user capabilities, making misuse potentially impactful.
From the tool's definition Tool name "upsertEntityGrantWithId" with description stating it "Creates or updates an Entity Grant" — explicit Write operations (create/update) with no indication of irreversible deletion.
Attacks that exploit this kind of access
The rule that runs upsertEntityGrantWithId 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 upsertEntityGrantWithId, this is the rule to start with:
upsertEntityGrantWithId 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 upsertEntityGrantWithId call is checked against it from then on.
Questions about upsertEntityGrantWithId
Creates or updates an Entity Grant. This is when a User/Entity is granted permissions to an Entity. 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 upsertEntityGrantWithId: 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.
upsertEntityGrantWithId 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 upsertEntityGrantWithId 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 upsertEntityGrantWithId. 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.
upsertEntityGrantWithId 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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