Cash Flow

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

Annotations already establish read-only and non-destructive behavior. The description adds a meaningful detail by saying totals come from YNAB's monthly figures rather than re-adding transactions, but it stops short of describing response format, currency, or any other runtime behavior.

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?

Two sentences, no filler; the core purpose is front-loaded and the second sentence justifies why the tool exists rather than relying on transaction-level data.

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 optional parameters fully documented and safety covered by annotations, the description supplies enough conceptual output detail (month-by-month income, spending, surplus) to invoke the tool confidently. It does not show explicit response shape, but no output schema exists and the tool is simple.

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?

Input schema descriptions cover all four parameters at 100%, so the description does not need to repeat parameter details. It adds no parameter-specific meaning beyond confirming the monthly framing.

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?

The description clearly identifies the resource as monthly income versus spending and the purpose is to reveal a surplus. It is distinguishable from transaction-listing and category/payee breakdown siblings by its month-level cash-flow framing, though it never names an alternative.

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?

The phrase 'so you can see whether you are running a surplus' gives a concrete use case. It does not enumerate when-not-to-use conditions or point to a specific sibling, but the context is clear enough for selection.

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