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mcp-ynab

mcp-ynab

by alexfu
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Remote

updateMonthCategory

Adjust the budgeted amount for a category in a given month within a YNAB plan. Specify the plan, month, category, and new assigned amount.

Instructions

Update a category for a specific month. Only budgeted (assigned) amount can be updated.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "plan_id": "<plan_id>",
      "month": "<month>",
      "category_id": "<category_id>",
      "category": "<category>"
    },
    "name": "updateMonthCategory"
  }
}

Input Schema

NameRequiredDescriptionDefault
monthYesThe plan month in ISO format (e.g. 2016-12-01) ("current" can also be used to specify the current calendar month (UTC))
plan_idYesThe id of the plan. "last-used" can be used to specify the last used plan and "default" can be used if default plan selection is enabled (see: https://api.ynab.com/#oauth-default-plan).
categoryYes
category_idYesThe id of the category

Output Schema

NameRequiredDescriptionDefault
dataYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A3.5/5.0
Behavior2/5

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It does clarify that only `budgeted` can be updated, but it does not state whether the update is partial or full, how non-budgeted fields are treated, required permissions, or error behavior. For a mutation endpoint, this is thin.

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 short sentences with no filler; the key constraint is front-loaded immediately after the verb. Every word earns its place.

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

Completeness3/5

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

The schema and output schema carry most of the calling details, and the description covers the one critical constraint. Missing are explicit when-to-use guidance and side-effect semantics, but these are not required to construct a syntactically correct call given the schema richness.

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?

The schema already documents all four parameters with formats and special values (`month` ISO/'current', `plan_id` 'last-used'/'default', `budgeted` milliunits), so the baseline is 3. The description adds the meaningful constraint that `budgeted` is the only mutable field, which helps explain the purpose of the nested `category` object.

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 states the specific verb 'Update', the resource 'a category for a specific month', and the only allowed field (`budgeted`). This clearly differentiates it from siblings like `updateCategory` (category-wide) and `getMonthCategoryById` (read).

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

Usage Guidelines3/5

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

The description implies this is the tool for month-scoped category budget changes and limits updates to `budgeted`, but it does not explicitly state when to prefer it over `updateCategory` or mention preconditions like plan/month existence. Usage guidance is present but entirely implied.

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

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