This record as markdown: /tools/io-fusionauth-mcp-api/updateformwithid.md
What updateFormWithId does on Fusionauth
AI agents use updateFormWithId 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 updateFormWithId is rated Medium
The 'update' action modifies form data reversibly without deleting it or executing arbitrary code. This is a Write operation. Severity is medium because malicious form modifications could affect authentication flows, user registration, or identity verification processes in a FusionAuth system, but the impact is limited to data modification rather than deletion or system compromise.
From the tool's definition Tool description states 'Updates the form with the given Id', indicating a modification operation that changes existing form data.
Attacks that exploit this kind of access
The rule that runs updateFormWithId 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 updateFormWithId, this is the rule to start with:
updateFormWithId 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 updateFormWithId call is checked against it from then on.
Questions about updateFormWithId
Updates the form 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 updateFormWithId: 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.
updateFormWithId 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 updateFormWithId 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 updateFormWithId. 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.
updateFormWithId 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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