YNAB MCP Server

List Categories

list_categories

Read-onlyIdempotent

Retrieve all category groups and categories with budgeted, activity, and balance amounts for the current month to locate category IDs and survey budget structure. Flags hidden, deleted, and internal items for filtering.

Instructions

List all category groups and their categories with budgeted/activity/balance amounts (dollars) for the current month. Read-only. Use to find category IDs and survey the budget structure; for a specific month's numbers use get_month, and for name-based lookup use search_categories. Hidden, deleted, and YNAB-internal items (e.g. Credit Card Payments, Internal Master Category) are included with 'hidden' / 'deleted' / 'internal' flags — filter on them when presenting.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`budgetId`	No	Budget ID (uses default if not provided)
`lastKnowledgeOfServer`	No	Delta request server knowledge. When provided, returns { category_groups, server_knowledge }.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv5.4.0Sep 15, 2026
- removedOutput schema / properties / result / description
```
Removed value: -"Structured result returned by List Categories."
```
Addedv5.2.0Aug 29, 2026
Removedv5.1.1Jul 21, 2026
First observedv2.0.0May 28, 2026

TDQS

A4.4/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover read-only/idempotent/safe, so the description's main added behavior is that hidden, deleted, and YNAB-internal items are included with flags. The current-month scope and the instruction to filter on flags provide useful behavior beyond the structured fields. No contradiction with annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is front-loaded with the core action and contains the alternative tools and hidden-item behavior in a compact form. 'Read-only' is slightly redundant with the annotations, but the four sentences are otherwise dense and useful.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 2-parameter, read-only list tool with a full output schema and 100% parameter documentation, the description is complete. It covers scope, alternatives, return contents, and special items, so an agent can invoke it correctly without digging further.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents both optional parameters. The description doesn't add parameter-level detail beyond that, which is acceptable under the baseline for fully documented schemas.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific action and object: 'List all category groups and their categories with budgeted/activity/balance amounts (dollars) for the current month.' It clearly distinguishes this from get_month and search_categories by naming those siblings, and it does not just restate the title.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives explicit use cases: find category IDs and survey the budget structure. It names get_month for a specific month's numbers and search_categories for name-based lookup, and it tells the agent to filter hidden/deleted/internal items when presenting. This leaves no ambiguity about when to select this tool.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.