AI agents call get_upcoming_json to retrieve information from Fantastical MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
get_upcoming_json retrieves upcoming calendar events in JSON format. This is a read-only query operation with no side effects—it does not modify, delete, or execute any actions. The low severity reflects that calendar data exposure is typically low-impact unless it contains highly sensitive scheduling information, but the tool itself performs only data retrieval.
From the tool's definition Tool name 'get_upcoming_json' and description 'Machine-readable variant of get_upcoming' indicate a retrieval operation.
Documented attack patterns abuse exactly the kind of access get_upcoming_json gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Fantastical MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for get_upcoming_json:
{
"version": "1",
"default": "deny",
"tools": {
"get_upcoming_json": {}
}
}get_upcoming_json is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Machine-readable variant of get_upcoming. It is categorised as a Read tool in the Fantastical MCP MCP Server, which means it retrieves data without modifying state.
Register the Fantastical MCP server in PolicyLayer and add a rule for get_upcoming_json: 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 Fantastical MCP. Nothing to install.
get_upcoming_json is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the get_upcoming_json 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 get_upcoming_json. 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.
get_upcoming_json is provided by the Fantastical MCP server (jaydenk/fantastical-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Fantastical MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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16 Fantastical MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.