mcp-ynab

by alexfu

Overview Schema Source Related Servers Discussions Admin

Python

Remote

createCategoryGroup

Create a new category group in your YNAB budget by specifying the plan ID and group name.

Instructions

Creates a new category group

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>",
      "category_group": "<category_group>"
    },
    "name": "createCategoryGroup"
  }
}

Input Schema

Name	Required	Description	Default
`plan_id`	Yes	The 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)
`category_group`	Yes

Output Schema

Name	Required	Description	Default
`data`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 15, 2026

TDQS

C2.9/5.0

Behavior2/5

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

With no annotations provided, the description must fully disclose behavioral implications. It only states 'creates', which implies mutation, but does not mention potential side effects, required permissions, or consequences like irreversible changes. The description fails to add behavioral context beyond the bare action.

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 description is a single, concise sentence with no redundant information. It is appropriately front-loaded and efficiently communicates the core purpose.

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 description is minimal but sufficient for a basic create operation when combined with the schema and output schema. However, the absence of usage guidelines and behavioral transparency makes it incomplete for an agent that needs to decide when to call this tool and what to expect.

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

Parameters2/5

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

The schema description coverage is 50%, with the plan_id and name parameters already documented in the schema. However, the description adds no additional parameter semantics and does not compensate for the category_group object lacking its own description. The agent must rely solely on the schema, which is partially incomplete.

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

Purpose4/5

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

The description clearly states the action (creates) and the resource (category group), making the tool's purpose unambiguous. However, it does not explicitly differentiate it from sibling tools like updateCategoryGroup or getCategories, though the resource name itself provides implicit differentiation.

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

Usage Guidelines2/5

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

The description provides no guidance on when to use this tool versus alternatives such as updateCategoryGroup or createCategory. It lacks context about prerequisites, typical scenarios, or any exclusions, leaving the agent to infer usage.

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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