This server lets you manage and analyze your Yahoo Fantasy Baseball team through an AI assistant, integrating Yahoo Fantasy data with advanced stats from MLB, Baseball Savant, and FanGraphs.
Authentication & Setup
Check setup status, start OAuth login, complete authorization, log out/reset, and set your default league/team.
League & Team Info
List all leagues, get league overviews, view standings, fetch scoring categories, and see recent transactions (adds, drops, trades).
Roster Management
View your roster with slot/injury status, with or without stats. Get aggregated team stats by week or full season.
Matchups & Scoreboard
View the league scoreboard for any week, or a specific team's matchup history across the season.
Player Research
Search players by name, rank/browse free agents and rostered players by any stat, get player stats for specific dates, and list MLB probable starting pitchers with optional fantasy ownership context.
Advanced Analytics
Deep-dive on individual players or your entire roster using Statcast (xBA, xSLG, xwOBA, exit velocity, barrel rate), FanGraphs (WAR, wRC+, FIP, K%, BB%), and MLB Stats API splits — all tailored to your league's scoring categories.
Fetches player statistics and advanced metrics from the MLB Stats API, including traditional stats (G, PA, HR, RBI, R, SB, BA, OBP, SLG, OPS, BABIP) and Statcast data (exit velocity, barrel rate, expected stats like xBA, xSLG, xwOBA, sprint speed) via integration with Baseball Savant and FanGraphs.
Click on "Install Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type @ followed by the MCP server name and your instructions, e.g., "@Yahoo Fantasy Baseball MCP Server show my roster and player stats"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
Manage your Yahoo Fantasy Baseball team from Claude or Codex with built-in skills for daily roster reviews, weekly post-mortems, automated lineup adjustments, and free-agent scouting.
All Yahoo league reads and writes run through a signed-in browser: Claude in Chrome or the Codex Browser plugin. The supported workflow does not use the Yahoo Fantasy Sports API.
The MCP server remains useful for saving the browser-discovered default team and for deeper player-performance analysis through the MLB Stats API, Baseball Savant Statcast, and FanGraphs.
Yahoo has revoked Fantasy Sports API access for unverified developers. This project therefore uses a signed-in browser for all Yahoo league data and actions; the preserved Yahoo API code is not used in the supported workflow.
Related MCP server: flaim
Pick the app you use — you only need one. Then continue to Connect your Yahoo team.
1. Add the extension
Download fantasy-baseball-vX.X.X.mcpb from the Releases page.
In Claude Desktop, go to Settings → Extensions.
Drag the file into the Extensions window and click Install.
2. Add the Fantasy Baseball skill (guided start/sit and roster-review workflow)
Download fantasy-baseball-skill-vX.X.X.zip from the Releases page.
Go to Settings → Capabilities and turn on code execution.
Go to Customize → Skills, click + → Create skill → Upload a skill, and choose the ZIP.
Requires Node.js (nodejs.org/download — install the LTS build). The plugin bundles the public analysis tools and the Fantasy Baseball skill in one step.
In the Codex app, go to Settings → Plugins → Add plugin marketplace.
Add from a GitHub repo:
Source: dingyiyi0226/fantasy-baseball-mcp
Git ref: master
Sparse paths: (leave blank)
Open the Fantasy Baseball marketplace and install the Fantasy Baseball plugin.
Continue to Connect your Yahoo team.
No Yahoo developer app, Client ID, Client Secret, or OAuth setup is needed.
In a Codex chat, ask:
Open https://baseball.fantasysports.yahoo.com in the in-app browser so I can sign in.Sign in to Yahoo in that in-app browser. Keep the session there; all roster, matchup, player, transaction, lineup, and add/drop workflows use it.
Connect Claude in Chrome, open https://baseball.fantasysports.yahoo.com, and sign in to Yahoo in
that connected Chrome browser.
Then ask show my Yahoo fantasy teams. The skill discovers the visible leagues and teams from the
browser. If more than one team is available, choose one; the MCP server saves that
browser-discovered team as the local default.
If Yahoo is signed out later, the workflow stops and asks you to sign in in the same browser. It does not fall back to OAuth or the Yahoo API.
Say this... | To do this |
| Show your current roster |
| Summarize this week's matchup |
| Show league standings |
| Find free-agent targets |
| List probable starters; add “who's a free agent?” to check availability |
| Compare recent performance with Statcast and FanGraphs indicators |
| Makes one approved lineup swap in the signed-in Yahoo browser, then verifies it saved |
| Applies the agreed start/bench moves from a roster review |
| Adds that exact free agent when there is an open roster spot |
| Submits only that exact approved add/drop pair and verifies the resulting roster |
| Reviews the current matchup, lineup, open slots, and free-agent or streamer opportunities |
| Recommends exact start/bench swaps and explains why |
| Grades lineup choices, adds/drops, and category strategy for this week or the week just finished |
| Identifies realistic category flips and the best remaining path |
Yahoo actions use the signed-in session in Codex's in-app browser or Claude's connected Chrome. They stop if Yahoo is not signed in or the requested move is ambiguous. You can always ask for advice first; an add/drop is submitted only after you explicitly approve the exact player or pair.
The MCP server is still used for public player analysis and the locally saved default Yahoo team. Browser-only roster and matchup reads can work from the skill without Yahoo API credentials.
The current browser owns the Yahoo login session. The local config stores only the browser-discovered default league/team identifiers for the supported workflow.
Legacy Yahoo OAuth/API code remains in the package for possible future compatibility, but normal startup does not register or use it.
For batters, we use season, 14-day, and 30-day splits; xBA, xSLG, xwOBA, and their expected-vs-actual gaps; exit velocity, hard-hit rate, barrel rate, launch angle, sweet-spot rate, and batted-ball distance; WAR, wRC+, wOBA, ISO, BABIP, K%, BB%, SwStr%, GB%, FB%, HR/FB, and LD%.
For pitchers, we use season, 14-day, and 30-day splits; xBA, xSLG, and xwOBA allowed; exit velocity, hard-hit rate, barrel rate, and launch angle allowed; WAR, ERA, FIP, xFIP, WHIP, K%, BB%, SwStr%, GB%, FB%, HR/FB, BABIP, and LOB%.
MIT
Unclaimed servers have limited discoverability.
If you are the server author, to access and configure the admin panel.
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