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

With no annotations the description carries the full burden, and it delivers: it discloses the comparison model (same monthly amount, highest rate first, 0% promo aware), that origination fees and shortfall/extra cash are included, and that early payoff and a fee-offer crossover month are surfaced. It does not describe return structure or units, but this is a side-effect-free calculator so the safety gap is minimal.

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?

Front-loaded with the decision question, then the comparison mechanics and outputs. Dense but every clause (fees, shortfall/extra cash, payoff month, crossover month) adds distinct information; only the trailing 'no credit data' is slightly redundant filler.

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 4-parameter, no-output-schema tool, the description covers the decision it answers, the inputs it consumes, and the shape of the results (per-payoff-month interest+fees, fee-breakdown month). Exact return fields are unspecified, but an agent has enough to select and invoke it correctly.

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 50%, and the description compensates meaningfully — 'same monthly amount' explains monthly_budget, '0% promo aware' explains apr_after_promo/promo_months_left, and 'up to two loan offers' matches the maxItems=2 constraint. It doesn't clarify the interest_rate vs APR distinction beyond what the schema already states.

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 concrete comparison task — paying cards directly vs up to two personal-loan offers — with specific outputs (interest+fees by payoff month, crossover month). It is clearly distinct from debt_avalanche_plan, though it never names or contrasts with that sibling explicitly.

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 framing question ('Should you consolidate credit cards with a personal loan?') implies when the tool applies, and the closing 'Deterministic arithmetic; no credit data' scopes it. But there is no explicit when-not-to-use guidance or pointer to an alternative sibling.

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