YNAB MCP Server

List Months

list_months

Read-onlyIdempotent

List budget months with monthly totals for income, budgeted, activity, Ready to Assign, and age of money. Use to see which months exist and their headline totals before drilling into a specific month.

Instructions

List all budget months with summary numbers per month (income, budgeted, activity, Ready to Assign, age of money — dollars). Read-only. Use to find which months exist and their headline totals; for per-category detail in one month use get_month.

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 { months, 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 Months."
```

Changed1 schema field changedv5.1.1Jul 21, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "result": {
+      "description": "Structured result returned by List Months."
+    }
+  },
+  "required": [
+    "result"
+  ],
+  "type": "object"
+}

First observedv2.0.0May 28, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds contextual value by explaining the dollar-unit summary metrics and the tool's scope across all months, which goes slightly beyond the structured annotations.

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?

Two well-structured sentences with no wasted words. The core behavior is stated first, followed by a precise routing note to the alternative tool.

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 simple read-only listing tool with an output schema, rich annotations, and optional parameters, the description fully covers what an agent needs to select and call it correctly. The delta parameter behavior is documented in the schema.

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 fully documents both parameters. The description does not elaborate on parameter behavior beyond what the schema provides, meriting the baseline score.

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 uses a specific verb ('List') with a precise resource ('all budget months') and enumerates the summary fields returned. It clearly differentiates from the sibling get_month by noting this is the month-level overview tool.

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 explicitly states when to use the tool ('find which months exist and their headline totals') and names the alternative for per-category detail ('use get_month'). This gives an agent clear routing guidance with no inference needed.

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