Connect an assistant

Every app uses the same server URL. The first time you connect, you’ll see an MCP Cubby screen: tap Start instantly for a guest cubby, or sign in with email.

MCP server URL

Claude (web, desktop, mobile)

Open Settings → Connectors.
Choose Add custom connector, name it “MCP Cubby” and paste the URL.
Click Connect and finish on the MCP Cubby screen.

ChatGPT

Open Settings → Apps & Connectors and turn on developer mode under Advanced.
Create a connector with the URL above and OAuth authentication.
Connect and finish on the MCP Cubby screen.

Menu names change from time to time. Look for “custom connector” or “MCP server”.

Claude Code

claude mcp add --transport http mcp-cubby https://mcpcubby.com/mcp

Then run /mcp inside Claude Code to sign in.

Cursor, VS Code, other clients

{
  "mcpServers": {
    "mcp-cubby": { "url": "https://mcpcubby.com/mcp" }
  }
}

Headless agents (no browser)

Create a guest cubby and API key in one call, then send the key as a bearer token. Give the returned claim_url to the person the agent works for.

curl -X POST https://mcpcubby.com/api/agents/register \
  -H "Content-Type: application/json" -d '{"agent_name": "Coach bot"}'

curl -X POST https://mcpcubby.com/mcp \
  -H "Authorization: Bearer cub_k_…" -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"cubby_whoami","arguments":{}}}'

Signed-in users can also create agent keys under Connections. Plain-text guide: /llms.txt.

Tools

Tool	What it does
`cubby_whoami`	Shows the cubby this connection writes to: whether it is claimed by a person or still a guest, preferred units and timezone, installed modules, and (for guests) the claim_url the user should open to keep their data and see the dashboard. Call this first in a new conversation.
`cubby_set_preferences`	Updates the user's preferences: weight units (kg or lb, used for all results), IANA timezone (e.g. "Pacific/Auckland", used to decide what "today" is), and display name.
`fitness_log_workout`	Permanently saves a completed workout. Call this whenever the user tells you about training they did, then confirm what was saved. Give each set individually in "sets", or use the shorthand set_count + reps + weight for identical sets ("3x5 at 100kg"). Common exercise aliases are merged ("bench" = "Bench Press"). Returns totals per exercise and any NEW PERSONAL RECORDS. Re-sending the identical workout within 15 minutes is detected and not saved twice. To fix a mistake, call fitness_delete_workout and log it again.
`fitness_get_workouts`	Returns logged workouts (newest first) with every set, optionally filtered by date range and/or exercise. Use it to answer "what did I do on…" questions exactly.
`fitness_delete_workout`	Removes a logged workout (by workout_id from fitness_get_workouts or fitness_log_workout) from history, records and totals. Use it to correct mistakes.
`fitness_exercise_history`	Session-by-session history for one exercise: every set, top set, volume and estimated 1RM per session, plus the trend across the period.
`fitness_personal_records`	All-time bests from the log: heaviest working set, best estimated 1RM and most reps, with dates. Optionally for one exercise.
`fitness_training_summary`	Totals for the last N days: sessions, working sets per muscle group, volume per exercise, training frequency and days since the last workout.
`fitness_suggest_next`	Deterministic progressive-overload suggestion (double progression) for an exercise, based on the last sessions in the log: add weight when every set hits the top of the rep range, add reps when inside it, repeat or deload after misses. Explains the reason.
`fitness_list_exercises`	Every exercise the user has logged, with session counts and last date. Use these names when logging so history stays together.
`fitness_log_body_metrics`	Saves body weight, body-fat % and/or waist measurement for a day, and returns the recent trend.
`fitness_body_metrics_history`	Body weight / body-fat / waist entries for the last N days with the weekly rate of change.
`fitness_set_profile`	Stores the facts needed for energy calculations: sex, birth year, height, activity level and goal. Only the fields given are changed.
`fitness_calc_energy`	BMR (Mifflin–St Jeor), maintenance calories (TDEE), a goal calorie target and protein/fat/carb grams. Uses the stored profile and latest body weight; any argument overrides them.
`fitness_calc_one_rep_max`	Estimated 1RM from a set (weight × reps) using six standard formulas, plus a table of target weights for 1–12 reps. Pure calculation; nothing is saved.
`fitness_calc_plates`	Which plates to load on each side of the bar to reach a target weight. Pure calculation; nothing is saved.