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alexfu

mcp-ynab

by alexfu

createCategory

Create a new budget category in YNAB by specifying its name, category group, and optional goal targets or notes. Use this to organize finances and track spending goals.

Instructions

Creates a new category

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
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

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
dataYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

B3.1/5.0
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 only indicates a mutating action ('Creates') but does not mention side effects, required permissions, failure modes, or what the response contains.

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

Conciseness4/5

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

The description is a single, direct sentence with no filler and is appropriately front-loaded. It is slightly under-specified, but the brevity is not itself a structural defect.

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

Completeness2/5

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

Despite having an output schema and a fairly detailed input schema, the description is minimal for a mutating tool of moderate complexity. It does not explain required relationships (e.g., category_group_id), goal-field behavior, or when creation is appropriate, so an agent is left without sufficient high-level context.

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 description adds no parameter-level meaning, but the schema already documents plan_id and most of the category object's fields in reasonable detail. At 50% schema coverage, the description does not meaningfully compensate, yet the schema provides enough to keep this at a baseline level.

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 and resource ('Creates a new category'), which clearly states what the tool does. It is readily distinguishable from siblings like updateCategory, getCategories, and createCategoryGroup, so an agent can tell them apart without deeper inspection.

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 gives no guidance about when to use this tool versus alternatives like updateCategory or createCategoryGroup. It also omits any prerequisites or context about how category creation relates to plans or category groups.

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