Month summary

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

Annotations already declare readOnlyHint and idempotentHint, but the description adds real context beyond them: amounts are in currency units, activity is negative for spending, only overspent categories appear, and it costs a single YNAB request and mutates nothing. Return shape/pagination is left to the output schema.

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

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

Three compact sentences, front-loaded with the summary contents before the routing list. The sibling-comparison clause is dense but each part maps to a distinct decision, so little is wasted.

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

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

With an output schema present and annotations covering safety, the description only needs to convey scope and semantics — the sign convention, currency units, and overspent-only listing are exactly the gaps it fills. Nothing an agent needs to call it correctly is missing.

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

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

Schema description coverage is 100%, so both plan_id and month (including the 'YYYY-MM-01'/'current' format) are already documented in the schema. The description adds no parameter syntax or defaulting detail beyond that, so the baseline of 3 applies.

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

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

States a specific verb+resource (month summary) and enumerates the exact contents (income, budgeted, spent, Ready to Assign, overspent categories), which lets an agent distinguish it from sibling tools without opening a schema.

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

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

'Use it first to review a month' gives explicit ordering guidance, and it names three alternatives with the conditions that select them: get_category_balances for all categories, get_spending_trends for prior-month comparison, forecast_balance for future months.

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