List all fantasy leagues (and game weeks / stat categories) for the logged-in Yahoo account. Use this to discover league_key and team_key values.
AI agents call list_leagues to retrieve information from Yahoo Fantasy Baseball without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool retrieves and queries league information for the authenticated user. It does not create, modify, delete, or execute operations—it simply lists existing data to enable discovery of identifiers for use by other tools. This is a classic Read operation with minimal risk, appropriate for an AI agent to call safely.
From the tool's definition Tool description states it 'List[s] all fantasy leagues' with the explicit purpose to 'discover league_key and team_key values', which is a retrieval operation with no side effects.
Attacks that exploit this kind of access
List all fantasy leagues (and game weeks / stat categories) for the logged-in Yahoo account. Use this to discover league_key and team_key values. It is categorised as a Read tool in the Yahoo Fantasy Baseball MCP Server, which means it retrieves data without modifying state.
Register the Yahoo Fantasy Baseball MCP server in PolicyLayer and add a rule for list_leagues: 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 Yahoo Fantasy Baseball. Nothing to install.
list_leagues 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 list_leagues 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 list_leagues. 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.
list_leagues is provided by the Yahoo Fantasy Baseball MCP server (yahoo-fantasy-baseball-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
list_leagues is one line of Yahoo Fantasy Baseball's registry record.
The record carries the whole server: verified identity, auth posture, risk grade, every tool classified, recommended policy — re-checked continuously.
Teams ship this data inside their own products. See what a licence covers →