arcade-ynab-mcp

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CreateCategory

Ynab_CreateCategory

Creates a YNAB category within a specific group, optionally with a spending target. Simplifies adding and organizing budget categories.

Instructions

Create a category in a category group, optionally with a target (goal).

Input Schema

TableJSON Schema

Name	Required	Description
`name`	Yes	The new category's name.
`note`	No	Optional note.
`plan_id`	No	The YNAB plan (budget) ID. Defaults to 'last-used', the plan the user opened most recently. Use ListPlans to find other plan IDs.
`goal_target`	No	Target amount in currency units. Creates a 'Needed for spending' target if the category has none.
`goal_frequency`	No	Make the target repeat monthly, weekly or yearly. Requires goal_target.
`goal_target_date`	No	Target date (YYYY-MM-DD). Can't combine with frequency.
`category_group_id`	Yes	The category group to put it in. Use ListCategories to find group IDs.
`goal_needs_whole_amount`	No	true = 'Set aside another' the target each period; false = 'Refill up to' the target.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.3.0Oct 4, 2026

TDQS

C2.9/5.0

Behavior2/5

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

Annotations already declare readOnlyHint=false, idempotentHint=false, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds nothing beyond that: it does not warn that repeated calls create duplicate categories despite idempotentHint=false, nor mention permissions, errors, or whether a goal can later be modified.

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?

A single front-loaded sentence with no filler or repetition. It is efficient, though it is arguably too terse for an 8-parameter mutation tool where a clause on goal interaction would earn 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?

An output schema exists and the parameter schema is fully documented, so return values and argument semantics need not be repeated. What is missing is usage context: when creating a category is appropriate versus updating an existing one, and the duplicate-creation behavior implied by non-idempotence.

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% across all 8 parameters, and the schema already explains goal_target creating a 'Needed for spending' target, the frequency/date mutual exclusion, and ID lookups. The description's phrase 'optionally with a target (goal)' is weaker than what the schema already provides, so baseline 3 applies.

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?

States a specific verb+resource (create a category) plus its placement constraint (in a category group) and an optional capability (target/goal). It does not differentiate itself from siblings like CreateCategoryGroup or CreatePayee, but the action itself is unambiguous.

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?

No when-to-use guidance, no alternatives named, no prerequisites or exclusions stated. The only routing help (use ListPlans / ListCategories to find IDs) lives in the schema descriptions, not the tool description.

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