fantasy-yolo

A fantasy football agent server. An MCP server and a matching CLI that let you — or an agent you run — read and manage your own ESPN Fantasy Football team.

$ fy check-lineup
1 thing(s) to look at across 9 starters
  projected_zero: Josh Jacobs (RB/WR/TE) is projected 0.0 points by ESPN

$ fy player "Saquon Barkley"
Saquon Barkley (RB, PHI) is rostered by The white Bhatoyas

Ask an agent "anything wrong with my lineup this week?" or "who has Saquon, and what are they thin at?" and get an answer from live league data.

The one thing to understand first

The human is the brain. This server has no optimizer, no projections model, and no opinion about which players are good. It answers questions accurately and executes instructions carefully. It will tell you a starter is projected zero points; it will never tell you to bench him.

That is a deliberate constraint, not a missing feature. See Why no optimizer.

Related MCP server: Sleeper MCP Server

Install

Needs Python 3.13 and uv.

git clone https://github.com/gagandaroach/fantasy-yolo
cd fantasy-yolo
uv sync
uv run fy --help

Then follow docs/setup.md — two cookies out of your browser and a small config file naming your league. Five minutes.

As an MCP server

{
  "mcpServers": {
    "fantasy-yolo": {
      "command": "uv",
      "args": ["run", "--directory", "/path/to/fantasy-yolo", "fantasy-yolo-mcp"]
    }
  }
}

No credentials in that stanza — deliberately. They live in a chmod 0600 file the config points at.

Tools

Every tool is available identically over MCP and on the CLI, generated from one definition, so the two cannot drift apart.

Reading — always available

Writing — off by default

Set write_enabled: true in your config to turn these on. While it's false they are not registered at all, so a model cannot see or offer them.

Trades are designed but not yet built.

How writes are made safe

ESPN's transaction API has no dry run and no idempotency key. A retried write genuinely submits the move a second time. Everything below exists because of those two facts.

Two calls, one code. Every write is split. preview_* shows the change in player names and returns a short-lived, single-use code bound to that exact transaction. execute_* refuses to run without it. An approval given for one add cannot be spent on another, and a retried execute is refused rather than double-submitted.

Being honest about what that guarantees. It makes a write impossible as a side effect of a question, and forces the preview into the transcript. It does not guarantee a human read it — a model can call preview and execute in the same turn. The real human-in-the-loop guarantee is your MCP client's approval prompt on a tool marked destructiveHint. We set that annotation; your client decides what to do with it.

Nothing is ever retried. Retries are disabled at the HTTP adapter, because requests and urllib3 retry by default and this is the one platform where that silently double-submits a waiver claim. A timeout is reported as unknown — never as success, never as failure — with your roster re-read so you can see for yourself.

Your roster is re-read immediately before every write. If anything moved since the preview — you set a lineup on your phone — the write is refused rather than silently clobbering it.

Legality is checked client-side, since ESPN won't tell you in advance: roster space, slot eligibility, whether a player is actually free or actually yours, your bid against your remaining budget and the league minimum, and whether your league even uses FAAB.

It can only ever touch your own team. isLeagueManager and isActingAsTeamOwner are hard-wired false with no parameter exposing them, and your team id is pinned in config.

Every write is logged — intent before the request leaves, outcome after — so an interrupted write still leaves something to reconcile against. Credentials are redacted from every line.

What this server does not know

Stated in the server's own instructions, so a model driving it is told up front rather than left to invent:

• No projections beyond ESPN's own number. There is no model here.

• No injury news, no news feed, no reporter text.

• No timestamps on injury designations. ESPN reports a status word and nothing else. It will catch a player ruled out on Wednesday; it will not catch a Sunday-morning inactive.

• No ranking of players on merit.

A missing projection is returned as null, never as 0.0 — because ESPN really does project some players at zero, and conflating the two invites a confident wrong conclusion.

Why no optimizer

Removing the optimizer doesn't remove decision-making from the product — it moves it to you, where the context is. An automated optimizer on this platform would also be operating with no dry run and no undo, which is a bad combination for irreversible moves.

There's a second reason worth naming: if you drive this with an LLM, the decision-making relocates into a general model with no current fantasy data. That model will fill silence with confident, plausible, wrong detail. Hence the section above — telling it loudly what it doesn't know is the compensating control.

Notes on ESPN's private API

Documented here because it is otherwise scattered across gists and half-wrong repos. All verified against live ESPN.

Three shapes most public implementations get wrong, all confirmed correct here by ESPN's own parser:

• A future-week lineup is FUTURE_ROSTER, not ROSTER.

• A standalone drop is ROSTER, not FREEAGENT.

• The trade verbs (TRADE_ACCEPT, TRADE_DECLINE, …) do exist.

A daily canary checks that ESPN still parses the exact payloads we'd send. ESPN tightened leagueHistory in Aug 2025 and split read/write hosts in Apr 2024, both without notice.

Design

• docs/user-stories.md — 101 stories, the ground truth

• docs/design.md — architecture, the write protocol, open questions

• docs/setup.md — getting your cookies

src/fantasy_yolo/
  espn/       vendored ESPN client (football), ours to fix
  read/       read wrappers + the raw fetches espn-api misses
  write/      payload builders, never-retry client, error interpretation
  policy/     lineup planner, legality, confirm tokens, audit log
  tools/      the 19 tools
  cli.py      Typer frontend      ─┐ both generated from one registry,
  mcp/        MCP frontend        ─┘ so they cannot drift

Status

Reads are working and verified against a live league.

Writes are proven. A six-item batched lineup change against a live 14-team league returned 200 EXECUTED on 2026-09-08. The confirmation token survived across two separate CLI processes, the re-read-before-write guard held, and the audit log captured intent and outcome with credentials redacted.

Add/drop and waiver writes are built and their payloads validated by ESPN's own parser, but have not yet been fired authenticated. Trades are designed, not built.

Before you use this

Unofficial. Not affiliated with, endorsed by, or sponsored by ESPN or Disney. It drives a private, undocumented API that can change or break without notice.

It runs on your machine, with your credentials, on your own account. It operates no service and redistributes nothing.

"Runs locally" is not "stays local." Everything this server returns is handed to whatever MCP client and model you configure — for most people, a hosted service. There is no telemetry and no network connection other than to ESPN, but that is not the same as your data staying on your machine.

What you're risking. ESPN's terms restrict unofficial automated access. ESPN can suspend or terminate your account and your league, and neither this project nor its author can restore anything they take. Read Disney's Terms of Use and ESPN's Fair Play and Conduct rules and decide for yourself. Note ESPN ships its own "Auto Control" AI that makes roster moves — automation is not itself against the spirit of the game — but that is not permission to drive the private API from outside.

espn_s2 is a full ESPN/Disney session cookie, not a scoped token. Leaking it is account compromise. Never paste it into an issue, a chat, or a screenshot.

Licence

MIT. Permissive: use it, change it, ship it, sell it. The only thing it asks is that the copyright notice travels with the code.

It covers this project's own code. It grants no rights to ESPN's data, marks, or API, and it is not permission from ESPN.

Vendored code

src/fantasy_yolo/espn/ is a vendored copy of the football half of espn-api by Christian Wendt, also MIT. Its licence is preserved verbatim at LICENSE-espn-api, as MIT requires when redistributing.

It is vendored rather than depended on so defects in the read path can be fixed directly. The first was a POSITION_MAP that could not convert a lineup slot label back to its id for bench, IR or flex — which made lineup writes impossible. Our changes are marked fantasy-yolo: in comments, and its own test suite runs in our CI.