startPasswordlessLoginWithId
Start a passwordless login request by generating a passwordless code. This code can be sent to the User using the Send Passwordless Code API or using a mechanism outside of FusionAuth. The passwordless login is completed by using the Passwordless Login API with this code.
This record as markdown: /tools/io-fusionauth-mcp-api/startpasswordlessloginwithid.md
What startPasswordlessLoginWithId does on Fusionauth
AI agents invoke startPasswordlessLoginWithId to trigger actions in Fusionauth. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call: builds kicked off, notifications sent, workflows started.
Why startPasswordlessLoginWithId is rated High
This tool executes an authentication workflow that generates credentials/codes and initiates login processes. While not destructive or financial, it performs an operation with external side effects (code generation, potential out-of-band communication) that could be misused to initiate unauthorized login attempts if an agent calls it with arbitrary user IDs.
From the tool's definition Tool description states it 'generates a passwordless code' and 'starts a passwordless login request', which triggers an external authentication operation.
Attacks that exploit this kind of access
The rule that runs startPasswordlessLoginWithId 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 startPasswordlessLoginWithId, this is the rule to start with:
startPasswordlessLoginWithId stays usable, but rate-capped: a runaway agent can't fire it dozens of times 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 startPasswordlessLoginWithId call is checked against it from then on.
Questions about startPasswordlessLoginWithId
Start a passwordless login request by generating a passwordless code. This code can be sent to the User using the Send Passwordless Code API or using a mechanism outside of FusionAuth. The passwordless login is completed by using the Passwordless Login API with this code. It is categorised as a Execute tool in the Fusionauth MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Fusionauth MCP server in PolicyLayer and add a rule for startPasswordlessLoginWithId: 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.
startPasswordlessLoginWithId is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the startPasswordlessLoginWithId 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 startPasswordlessLoginWithId. 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.
startPasswordlessLoginWithId 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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