YNAB MCP Server

Update transactions

update_transactions

DestructiveIdempotent

Modify existing YNAB transactions in one request: approve, categorize, fix payees, set memos, add flags, or mark cleared while leaving unchanged fields intact.

Instructions

Change one or more existing transactions in one request.

Each change names a transaction and only the fields to change; every other field stays as it is. This is the tool for reviewing transactions: approve them, categorize them, fix payees, set memos, flag them, or mark them cleared.

Example changes:

Approve and categorize: {id: , approved: true, category_id: }
Fix the payee: {id: , payee_name: "Costco"}
Clear the memo and the flag: {id: , memo: "", clear_flag: true}

Input Schema

Name	Required	Description	Default
`changes`	Yes	The changes, one per transaction (required)

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Oct 26, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Beyond annotations, the description discloses partial-update behavior ('only the fields to change; every other field stays as it is') and batch semantics ('one or more existing transactions in one request'). It does not explain atomicity, failure behavior, or permission requirements, but the annotations already carry destructive, idempotent, and readOnly hints.

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

Conciseness5/5

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

The definition is front-loaded with the core operation, then adds compact examples. The sentences and bullets are information-dense without being bloated.

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

Completeness4/5

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

Given full schema coverage, an output schema, and rich annotations, the description covers batch updates, partial updates, and common update scenarios. Missing atomicity or error-handling details are minor for this tool because structured fields already cover return and safety semantics.

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 every field, default, enum, and update constraint. The description's example changes reinforce usage but add little semantic detail beyond what the schema already provides, fitting the baseline 3 for high-coverage 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 verb and resource: 'Change one or more existing transactions in one request.' It scopes the operation to existing transactions and names concrete update types, making it distinguishable from create/delete transaction siblings.

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

Usage Guidelines4/5

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

It clearly states this is the tool for reviewing transactions and lists approve, categorize, fix payees, set memos, flag, and mark cleared. It does not explicitly name when not to use it or point to sibling alternatives, but the intended usage context is strong.

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