One id for the same bet.

How the ids work

• game_ and 10 characters is one real game. A postponement moves its start time, never its id.
• ins_ and 12 characters is one bet on one game, such as the Chiefs to win by more than 3.5 points. This is the id to store.
• Ids are never reused. Store them as they are: never build or parse one. The characters are digits and capital letters without I, L, O or U, and the CLI and the MCP server accept an id in any case.
• A readable slug such as nfl-2026-w03-kc-at-mia-spread-kc-3.5 works wherever an id does, but a slug may change and the id does not.
• A spread is one instrument seen from either side. “KC -3.5” and “MIA +3.5” share one id: its YES is the Chiefs winning by more than 3.5 points, and MIA +3.5 is its NO side. The explorer says which side your words asked for and which side of the market to buy.
• In soccer a draw is its own instrument, “Draw”. A club's win is another: the NO side of “ARS ML” is “LEE or draw”, because Arsenal not winning also pays on a draw.
• If an id ever stops answering, resolve the bet in words again to get the current one.

What it covers

• NFL and college football: full-game moneyline, spread and total.
• MLB: full-game moneyline, run line and total runs.
• NHL: full-game moneyline, puck line and total goals.
• NBA: full-game moneyline.
• Premier League: each club to win and the draw, plus spreads and total goals, all over 90 minutes plus stoppage time.

Lines are half points, so none can land exactly. Spreads and totals are added closer to the game, so a game far out may have only its moneylines. Halves, periods, team totals and player props have no ids yet, and the resolver answers no rows for them rather than guess.

From the command line

arena resolve turns words into ids, arena instrument reads one id, and arena game lists every id on a game. They work signed out, with arena-prediction-cli 0.5.0 or later.

npm install -g arena-prediction-cli
arena resolve "kc -3.5"
arena instrument ins_0123456789AB
arena game "chiefs dolphins"
arena games --date today

The id above is a made-up example of the format.

From an AI agent

The MCP server (npx -y arena-mcp-server, 0.5.0 or later) has the same lookups as tools. They work signed out too.

• resolve_market: a bet in words to instruments, with the side to buy.
• get_instrument: one instrument and its listings.
• get_game: every instrument on one game.
• list_games: upcoming games with their ids.

The full reference, with outputs and errors, is on /docs/instruments.