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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, and the description still adds real behavioral context: 'stores nothing, connects to no bank and pays nothing', the null-is-not-zero rule, the rule that bills are excluded from category totals, and the 'not financial advice' caveat. These are computation semantics an agent could not infer from the annotations.

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?

It is a single dense paragraph that front-loads purpose, then outputs, then edge-case rules, then safety caveats. Every sentence carries information, though the long compound sentences packing four or five clauses each make it slightly harder to scan than a bulleted structure would.

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 no output schema available, the description carries the full burden of explaining return values and does so item by item. All six optional parameters, the zero-required-input case, and the question-only fallback are accounted for.

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 coverage is 100%, so baseline is 3, but the description adds genuine meaning on top: a blank amount stays unknown rather than defaulting to zero, bills are not folded into category totals, and as_of drives the overdue/due-in-7-days logic. Currency, paid default, and per-field formats are left entirely to the schema.

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 opens with a specific verb-and-resource statement ('manual bill and budget planning, with no bank connection') and then enumerates exactly what comes back: a due-date-sorted checklist with unpaid totals, overdue/next-7-day flags, actual-minus-planned per category, and the plan difference. An agent knows precisely what this tool produces without opening the 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?

It clearly delineates the two operating modes: supply bills and/or income and categories to get computed results, or supply only a question to get setup guidance. There are no sibling tools to route against, so the only missing piece is explicit guidance on when not to use it.

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