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Yahoo Fantasy Baseball MCP Server

Yahoo Fantasy Baseball MCP Server

by dingyiyi0226
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Local

Fantasy Baseball for Claude & Codex

npm

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.

WARNING

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.

Contents

Related MCP server: Yahoo Fantasy Baseball MCP

Install

Pick the app you use — you only need one. Then continue to Connect your Yahoo team.

Claude Desktop

1. Add the extension

  1. Download fantasy-baseball-vX.X.X.mcpb from the Releases page.

  2. In Claude Desktop, go to Settings → Extensions.

  3. Drag the file into the Extensions window and click Install.

2. Add the Fantasy Baseball skill (guided start/sit and roster-review workflow)

  1. Download fantasy-baseball-skill-vX.X.X.zip from the Releases page.

  2. Go to Settings → Capabilities and turn on code execution.

  3. Go to Customize → Skills, click + → Create skill → Upload a skill, and choose the ZIP.

Codex desktop app

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.

  1. In the Codex app, go to Settings → Plugins → Add plugin marketplace.

  2. Add from a GitHub repo:

    • Source: dingyiyi0226/fantasy-baseball-mcp

    • Git ref: master

    • Sparse paths: (leave blank)

  3. Open the Fantasy Baseball marketplace and install the Fantasy Baseball plugin.

  4. Continue to Connect your Yahoo team.

Connect your Yahoo team

No Yahoo developer app, Client ID, Client Secret, or OAuth setup is needed.

Codex

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.

Claude

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.

Talk to your team

Say this...

To do this

fantasy show roster

Show your current roster

fantasy my matchup

Summarize this week's matchup

fantasy standings

Show league standings

fantasy who should I add?

Find free-agent targets

who's pitching tomorrow?

List probable starters; add “who's a free agent?” to check availability

analyze Shohei Ohtani

Compare recent performance with Statcast and FanGraphs indicators

move <player> from BN to <slot>

Makes one approved lineup swap in the signed-in Yahoo browser, then verifies it saved

set my lineup today

Applies the agreed start/bench moves from a roster review

add <free agent>

Adds that exact free agent when there is an open roster spot

add <free agent> and drop <player>

Submits only that exact approved add/drop pair and verifies the resulting roster

review my roster today

Reviews the current matchup, lineup, open slots, and free-agent or streamer opportunities

who on my bench should I start tonight?

Recommends exact start/bench swaps and explains why

weekly review

Grades lineup choices, adds/drops, and category strategy for this week or the week just finished

can I still win this week?

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.

Good to know

  • 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%.

License

MIT

Available Tools

5 tools
analyze_players_statsAnalyze advanced stats for multiple playersA
Read-only

Fetch MLB Stats, Baseball Savant, and FanGraphs analysis for up to 10 players. Use this after reading roster or free-agent names from the signed-in Yahoo browser. Within each player, mlbStats.columns names the aligned values in mlbStats.standard and the optional mlbStats.recent14d and mlbStats.recent30d arrays.

Inputs: playerNames (required), season.

analyze_player_statsAnalyze advanced player statsA
Read-only

Fetch and aggregate advanced statistics for a single player from MLB Stats, Baseball Savant, and FanGraphs. Use Yahoo's browser pages separately for league scoring, ownership, roster, and lineup context.

Inputs: playerName (required), season.

fantasy_get_preferencesGet fantasy browser preferencesA
Read-only

Get the locally saved default Yahoo league and team for browser-driven workflows. This does not inspect Yahoo or verify that the browser is signed in.

Inputs: no named parameters.

fantasy_set_default_teamSave default fantasy teamA

Save a Yahoo league and team discovered from the signed-in browser. This stores local identifiers only and does not call Yahoo.

Inputs: teamId (required), leagueId (required), teamName, leagueName.

list_probable_startersList probable starting pitchers for a dateA
Read-only

List every probable starting pitcher across MLB for a date, with opponent, home/away, and game time. This tool uses MLB Stats only. Read Yahoo ownership and availability separately from the signed-in Yahoo browser.

Inputs: date.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

Loading tool schema changelog…

    Deploy Server
    One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

    TDQS

    A4.2/5.0

    Scored across 5 tools

    Disambiguation4/5

    The preference tools are clearly distinguished (read vs write), and list_probable_starters is distinct. However, analyze_player_stats and analyze_players_stats overlap in function, differing only in player count, which could confuse an agent. Descriptions help, but the boundary is not as crisp as it could be.

    Naming Consistency3/5

    Naming mixes a 'fantasy_' prefix for local preferences with bare action verbs for the stats tools, and the two analyze tools have inconsistent singular/plural forms. All names are snake_case and readable, but there is no unified pattern across the set.

    Tool Count5/5

    With 5 tools, the server is well-scoped for its niche purpose of fetching advanced stats and managing local preferences. Each tool serves a clear role, and the count feels neither thin nor bloated.

    Completeness4/5

    The server covers single-player and batch stats analysis plus probable starters, which aligns with its stated external-data focus. Minor gaps exist, such as no head-to-head player comparison or expanded roster operations, but these fall outside its apparent design.

    Maintenance

    ActivityStale
    ResponsivenessNo recent community issues

    Resources

    Related MCP Connectors

    Related MCP Servers

    • Yahoo Fantasy MCP

      andy78644
      F
      license
      Not graded
      quality
      D
      maintenance
      Enables Claude to interact with Yahoo Fantasy Baseball and Basketball leagues, allowing roster analysis, matchup tracking, free agent browsing, and player stats retrieval via natural language.
      -

    • baseclaw

      jweingardt12
      F
      license
      Not graded
      quality
      D
      maintenance
      Manages Yahoo Fantasy Baseball teams via AI, allowing natural language queries for roster updates, trade analysis, waiver wire, and league insights.
      4
      -