YNAB MCP Server

List Months

ynab_list_months

Read-only

Lists every plan month since the plan began, with raw summary fields: income, budgeted, activity, Ready to Assign, age of money and the month note. For income-versus-spending questions over recent months, use ynab_cash_flow instead.

Instructions

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "ynab_list_months"
  }
}

Input Schema

Name	Required	Description	Default
`planId`	No	The plan ID (optional, defaults to YNAB_PLAN_ID; budgetId is a deprecated alias)
`budgetId`	No	Deprecated alias of planId (still accepted)

Schema Changelog

Changes observed during successful MCP inspections.

Changed5 schema fields changedv0.3.0Sep 22, 2026

removedInput schema / additionalProperties
```
Removed value: -false
```

addedInput schema / properties / budgetId / anyOf

Added value: +[
+  {
+    "description": "Deprecated alias of planId (still accepted)",
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

changedInput schema / properties / budgetId / description

Previous value: -"The ID of the budget (optional, defaults to YNAB_BUDGET_ID environment variable)"New value: +"Deprecated alias of planId (still accepted)"

removedInput schema / properties / budgetId / type
```
Removed value: -"string"
```

addedInput schema / properties / planId

Added value: +{
+  "anyOf": [
+    {
+      "description": "The plan ID (optional, defaults to YNAB_PLAN_ID; budgetId is a deprecated alias)",
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "The plan ID (optional, defaults to YNAB_PLAN_ID; budgetId is a deprecated alias)"
+}

Addedv1.0.0Jan 2, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already declare readOnly, non-destructive and openWorld, so safety is covered. The description adds real context beyond that: the result covers every month since the plan began and returns raw summary fields rather than aggregates. It does not mention ordering or whether results are paginated, which is the remaining gap.

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 sentences, no waste, with the scope-and-fields statement front-loaded ahead of the disambiguation pointer. Every clause carries information an agent needs.

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?

With no output schema, the description usefully names the returned fields and the time scope, and both optional params are covered by the schema. Only minor behavioral details (ordering, month format, pagination) are unstated.

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 coverage is 100% and both parameters (planId and its deprecated budgetId alias, with the YNAB_PLAN_ID default) are fully documented in the schema. The description says nothing about parameters, so baseline 3 applies — the schema does all the work.

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?

States a specific verb and resource (lists every plan month since the plan began) and enumerates the fields returned (income, budgeted, activity, Ready to Assign, age of money, note). It also names the sibling it is not (ynab_cash_flow), so an agent can distinguish it without opening either schema.

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?

Gives an explicit exclusion with the alternative: for income-versus-spending questions over recent months, use ynab_cash_flow instead. What is missing is a positive statement of when this tool is the right pick (e.g. historical month-by-month raw figures), leaving half the routing decision implied.

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