createToken
Exchange User Credentials for a Token. If you will be using the Resource Owner Password Credential Grant, you will make a request to the Token endpoint to exchange the user’s email and password for an access token. OR Exchange User Credentials for a Token. If you will be using the Resource Owner ...
This record as markdown: /tools/io-fusionauth-mcp-api/createtoken.md
What createToken does on Fusionauth
AI agents invoke createToken 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 createToken is rated High
This tool performs an OAuth token exchange operation - it takes credentials (username/password or refresh tokens) and produces access tokens. This is an external authentication operation with significant security implications. Misuse could allow an AI agent to authenticate as arbitrary users or exchange credentials to obtain tokens that grant access to protected resources.
From the tool's definition Exchange User Credentials for a Token... exchange the user's email and password for an access token... Exchange a Refresh Token for an Access Token
Attacks that exploit this kind of access
The rule that runs createToken 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 createToken, this is the rule to start with:
createToken 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 createToken call is checked against it from then on.
Questions about createToken
Exchange User Credentials for a Token. If you will be using the Resource Owner Password Credential Grant, you will make a request to the Token endpoint to exchange the user’s email and password for an access token. OR Exchange User Credentials for a Token. If you will be using the Resource Owner Password Credential Grant, you will make a request to the Token endpoint to exchange the user’s email and password for an access token. OR Exchange a Refresh Token for an Access Token. If you will be using the Refresh Token Grant, you will make a request to the Token endpoint to exchange the user’s refresh token for an access token. OR Exchange a Refresh Token for an Access Token. If you will be using the Refresh Token Grant, you will make a request to the Token endpoint to exchange the user’s refresh token for an access token. OR Exchanges an OAuth authorization code for an access token. Makes a request to the Token endpoint to exchange the authorization code returned from the Authorize endpoint for an access token. OR Exchanges an OAuth authorization code and code_verifier for an access token. Makes a request to the Token endpoint to exchange the authorization code returned from the Authorize endpoint and a code_verifier for an access token. OR Exchanges an OAuth authorization code and code_verifier for an access token. Makes a request to the Token endpoint to exchange the authorization code returned from the Authorize endpoint and a code_verifier for an access token. OR Exchanges an OAuth authorization code for an access token. Makes a request to the Token endpoint to exchange the authorization code returned from the Authorize endpoint for an access token. OR Make a Client Credentials grant request to obtain an access token. OR Make a Client Credentials grant request to obtain an access token. 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 createToken: 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.
createToken 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 createToken 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 createToken. 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.
createToken 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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