Ynab

YNAB through One

YNAB is a personal budgeting and financial planning platform that provides tools and APIs for managing accounts, transactions, budgets, and spending categories, allowing users and developers to track cash flow, automate budgeting workflows, and build integrations around household finance data.

One exposes YNAB through four MCP tools. The table below carries real action ids from One's knowledge base, so for a common operation you can skip search and go straight to reading the action's parameters.

How to run an action

1. Find the action in the table below, or call search_one_platform_actions with platform ynab if it is not listed.
2. Call get_one_action_knowledge with the action id. Do this every time, including for actions in this table. The table gives you the id, not the parameters.
3. Call execute_one_action with parameters copied from that knowledge.

Never guess a parameter name, a body field, or an enum value. The knowledge has the real schema, and a guessed field is either a 400 or a silent write of the wrong thing.

Before you start

Call list_one_integrations once and confirm YNAB is connected. If it is missing, the user has not connected it: say so and point them at https://app.withone.ai rather than reaching for raw HTTP.

Each connection carries an access field. If it reports {"policy": "methods", "methods": ["GET"]} the agent is read-only here, so plan a read-only answer instead of attempting a write that will be refused.

Before a write

Creates, updates, deletes and sends land on a real YNAB account and cannot be recalled. State the action and the specific target in one line before the first write in a task, and let the user stop you. Reads need no confirmation.

Actions

Transactions

Plans

ScheduledTransactions

Categories

Accounts

PayeeLocations

Payees

MoneyMovementGroups

MoneyMovements

CategoryGroups

PlanCategories

PlanCategoryGroups

PlanMonth

PlanMonths

PlanPayees

CategoryTransactions

User

PlanTransactions

When a call fails

The error comes from YNAB, not from One. A 400 or 422 means your parameters do not match the schema, so re-read the knowledge and fix the field. A 401 or 403 means the connection needs re-authorizing, which no retry will fix. A 404 means the id is not on this account. A 429 means slow down. Never retry a write more than once: the first attempt may have landed.

Full catalog: https://www.withone.ai/knowledge/ynab

Integration knowledge by One (withone.ai), licensed under One-Knowledge-1.0. Attribution must be preserved in derivative works.