completeWebAuthnLoginWithId
Complete a WebAuthn authentication ceremony by validating the signature against the previously generated challenge and then login the user in
This record as markdown: /tools/io-fusionauth-mcp-api/completewebauthnloginwithid.md
What completeWebAuthnLoginWithId does on Fusionauth
AI agents invoke completeWebAuthnLoginWithId 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 completeWebAuthnLoginWithId is rated High
This tool performs an authentication ceremony and logs a user in, which is an external operation with significant security implications. It's not a simple read or write — it executes a multi-step authentication flow that grants access to a user account. Misuse could allow unauthorized authentication or account takeover.
From the tool's definition Complete a WebAuthn authentication ceremony by validating the signature against the previously generated challenge and then login the user in
Attacks that exploit this kind of access
The rule that runs completeWebAuthnLoginWithId 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 completeWebAuthnLoginWithId, this is the rule to start with:
completeWebAuthnLoginWithId 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 completeWebAuthnLoginWithId call is checked against it from then on.
Questions about completeWebAuthnLoginWithId
Complete a WebAuthn authentication ceremony by validating the signature against the previously generated challenge and then login the user in. 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 completeWebAuthnLoginWithId: 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.
completeWebAuthnLoginWithId 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 completeWebAuthnLoginWithId 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 completeWebAuthnLoginWithId. 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.
completeWebAuthnLoginWithId 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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