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

With no annotations, the description carries the full transparency burden. It adds genuinely useful behavioral detail: the computation is local, deterministic, and month-by-month, with a comparison to minimum-only payments. It does not mention error cases (e.g., invalid APR, zero balance) but for a pure calculation this is a solid disclosure.

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?

The entire tool is described in one dense sentence with no wasted words: the topic, method, main outputs, and one notable guarantee ('All math local and deterministic') all earn their place. No redundant grammar or repetition; front-loading is strong.

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?

For a two-parameter calculation tool that yields no output schema, the description names the key outputs (debt-free date, interest comparison, extra $50 monthly effect) and the calculation style. It omits the exact output formatting and required-field validation details, but given the tool's simplicity and the if-schema available for input structure, an agent can call it without needing to know much else.

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 only 50%: only apr and extra_monthly have descriptions. The description helps by anchoring APR to the ordering rule ('highest APR first') and by referring to 'minimums' and the extra $50/month, which maps to the debts.minimum and extra_monthly fields. Yet it doesn't clarify balance semantics or add anything beyond the schema for fields like minimum, so it only partially compensates for the coverage gap.

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 'Debt payoff plan' and immediately names the exact behavior: avalanche ordering by highest APR, month-by-month simulation, and the key outputs (debt-free date, interest vs minimums, extra $50/mo effect). This distinguishes it from the sibling financial tools like real cash_runway and subscription_audit without needing to open 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 makes explicit what the tool computes, so a user asking for an avalanche payoff plan or prepayment scenario can easily infer this is the right path. However, it never names alternatives or adds a when-not-to-use clause, so the agent gets no guidance for choosing among the sibling calculators or counterpart avoidance.

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