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chrisguidry
by chrisguidry

Update category

update_category
DestructiveIdempotent

Modify a YNAB category by renaming it, editing its note, moving it to another group, or setting its target; only supplied fields are changed.

Instructions

Rename a category, change its note, move it to another group, or set its target. Only the fields given change.

To change what is assigned to a category, use assign_money or set_assigned.

Input Schema

NameRequiredDescriptionDefault
nameNoNew category name (optional)
noteNoNew category note (optional)
category_idYesCategory to update (required)
target_dateNoDate the target amount should be reached, for a balance by a date. Cannot be combined with target_frequency (optional)
target_amountNoTarget amount in currency units. Setting it on a category with no target creates a monthly NEED target (optional)
target_frequencyNoMake a repeating NEED target of target_amount every "weekly", "monthly", or "yearly". Requires target_amount (optional)
category_group_idNoGroup to move the category to (optional)
target_needs_whole_amountNoFor NEED targets, whether the whole target is needed every period (true) or the rollover counts toward it (false) (optional)

Output Schema

NameRequiredDescriptionDefault
idYesUnique category identifier
nameYesCategory name
noteNoCategory notes
activityNoActivity this month (negative = spending)
assignedNoAmount assigned this month
internalNoWhether YNAB manages this category itself. 'Inflow: Ready to Assign' is internal: categorize income to it.
availableNoAmount available to spend, including rollover
target_dateNoDate the target should be met, for targets with a date
target_typeNoTarget type: NEED (needed for spending, refills each period), TB (have a balance), TBD (have a balance by a date), MF (fund monthly), DEBT (pay down a debt)
target_amountNoTarget amount
category_group_idYesCategory group ID
target_underfundedNoAmount still needed this month to stay on track
category_group_nameNoCategory group name
target_overall_leftNoAmount still needed to meet the target this period
target_percentage_completeNoHow much of the target is funded, as a percentage

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A4.2/5.0
Behavior4/5

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

Annotations already declare destructiveHint=true and idempotentHint=true; the description usefully mitigates the destructive concern by stating 'Only the fields given change,' i.e. PATCH-style partial semantics, so the agent knows omitted fields are not wiped. It does not disclose permission requirements or what happens when a target is unset/null-passed, which matters given the destructive flag.

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 filler. The capability list and the partial-update guarantee are front-loaded before the alternative-routing sentence, so the most decision-relevant information comes first.

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?

For an 8-parameter mutation with annotations and an output schema, the description covers what can change and the non-destructive-by-default field scoping. It omits edge behavior an agent might need — clearing an existing target, permission/auth expectations, and effects of target changes on budgeting — but the schema covers the parameter-level detail.

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%, so every one of the 8 parameters (including the target_date/target_frequency conflict and target_frequency requiring target_amount) is already documented in the schema. The description only restates the field groups at a high level and leaves the key ambiguity unresolved: whether passing null clears a field versus omitting it. Baseline 3 is appropriate.

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 (update) plus the resource and enumerates exactly the updateable facets: rename, note, group move, target. It also explicitly names the adjacent capabilities handled elsewhere (assign_money, set_assigned), so an agent can separate this tool from siblings that also sound like 'changing a category'.

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?

Provides a clear routing rule for the most likely confusion: 'To change what is assigned to a category, use assign_money or set_assigned.' That is a genuine when-not clause naming alternatives. It does not cover other nearby cases (e.g., when to use create_category vs. this tool, or renaming a group via rename_category_group), so it stops short of fully explicit routing.

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