Fantasy football MCP server — use verified NFL stats inside ChatGPT and Claude
Muffed is the AI that reads all the football data and tells fans what's actually real. The Muffed MCP server puts that engine inside your assistant: add https://muffed.ai/api/mcp to ChatGPT, Claude, Claude Code, Cursor, or any MCP-compatible client, and your AI can call Muffed's verified NFL data directly — how a player's season actually went, the current read on what's real across the league, advanced-stat leaders, backfield depth, and what the metrics mean. Connect a Sleeper league and it can talk about your league too. No account, no API key, no cost.
What it does
Your assistant stops guessing about football and starts asking. Every number it gets back is one Muffed already verified against source data, with the same attribution and the same as-of date the site carries. When your AI answers with them, it can cite where they came from.
What makes it different from asking your AI directly
An AI answering from memory gives you a number from whenever its training stopped, with no source and no date. Muffed's tools return figures recomputed from play-by-play and charting data, dated, attributed, and linked to a page you can check. That's the entire point: verified, dated, and sourced beats confident.
It goes one step further than most data sources are willing to. verify_claim takes a figure your AI has already stated and checks it against the panel — confirming it, or handing back the real number when it disagrees. Muffed is the only NFL data source that will check your AI's work.
Add it to your assistant
Claude (web, desktop, mobile) — Settings → Connectors → Add custom connector → paste the URL below. There is no sign-in step, because there is nothing to authorize.
https://muffed.ai/api/mcp
Claude Code
claude mcp add --transport http muffed https://muffed.ai/api/mcp
ChatGPT — Settings → Connectors (or Developer mode) → add an MCP server → paste the same URL, no authentication.
Cursor, VS Code, and other MCP clients — add to your MCP config:
{
"mcpServers": {
"muffed": {
"type": "http",
"url": "https://muffed.ai/api/mcp"
}
}
}What your AI can ask for
| Tool | What it answers |
|---|---|
| get_current_insights | What Muffed thinks is actually real about the NFL right now — verified, dated, with the evidence |
| query_stat_leaders | League leaders on any verified metric, each with the rank its source gave it |
| get_player_metrics | Every verified figure Muffed holds for one player or team |
| compare_entities | Two players or two teams side by side on the metrics both have |
| get_metric_definition | What a metric measures, and which seasons it actually covers |
| list_metrics | Which metrics can be asked about at all — keys and coverage, no figures |
| verify_claim | Checks a stated figure against the verified panel and returns the real one if it disagrees |
| get_backfield | Who backs up a starting running back — and in-season, who replaces an injured one |
| sleeper_find_leagues | Your Sleeper leagues, from your username |
| sleeper_get_league | Your league's setup — teams, scoring format, roster slots, managers |
| sleeper_matchup_preview | Verified context on both sides of a matchup |
| sleeper_roster_stories | Your roster's players and what's verified about each |
| sleeper_standings_story | Where your league stands, derived from Sleeper's roster records |
Every tool is read-only: nothing writes, nothing changes, nothing about you is stored. We keep a short technical log of which tools get called — see our privacy policy.
Try asking
- “What does Muffed say is real about the NFL right now?”
- “Who leads the league in rushing yards over expectation?”
- “What is RYOE, and who's good at it?”
- “Who backs up Bijan Robinson?”
- “Compare Achane and Bijan on verified numbers.”
- “My Sleeper username is [name] — what's verified about my roster?”
Questions
Is it free?
Yes, and there is no account and no API key. It is rate-limited per IP so one caller cannot take it down.
Does it work with my ESPN or Yahoo league?
No — Sleeper only. Sleeper publishes a public read API, so loading a league is instant and needs no login. ESPN and Yahoo offer nothing comparable, and the alternative would be screen-scraping or handling your credentials, which we will not do. Nothing personal; there is just no door.
Will it tell me who to start?
No. Muffed does not do start/sit, lineup advice, projections, or draft grades — not here, not anywhere. The tools return what is verified about the players involved and let you decide. That is a permanent position, not a v1 limitation.
Where does the data come from?
Data via nflverse · NFL Next Gen Stats via nflverse · FTN Data via nflverse. League data comes from Sleeper's public API — via Sleeper. Every tool response carries its own attribution and date.
Why isn't draft-market data (ADP) in here?
Because the sources we use for it are licensed to cite, not to redistribute. We can quote a price on a page with credit, but we will not pipe someone else's data into your AI. Everything the tools serve is data we are licensed to build on.
How current is it?
Every response is stamped with its own as-of date, so you always know what you are looking at. Charting-derived figures cover the 2025 season only and say so. Season coverage varies by metric — rushing yards over expectation, for one, starts in 2018 rather than 2016, and asking outside that range returns the real coverage instead of a substitute.
Do you store my league?
No. A league id you give your assistant answers that request and is cached briefly to be polite to Sleeper's API. It is never written to our database and never linked to you. We keep a salted one-way hash of it for 30 days so we can count roughly how many distinct leagues use the server, and nothing else. Your Sleeper username is not logged at all.
Can I use this in something I'm building?
Individuals, freely. If you are calling it at volume or building it into a product, email hello@muffed.ai first so we can keep it up for everyone. The underlying nflverse data is CC-BY and free — what Muffed adds is verification, structure, freshness, and the story layer.
Support: hello@muffed.ai