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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantial operational context beyond them: no authorization required, a 60 req/min rate limit, ordering by site ranking rather than price, error behavior on an unknown region, and truncation signaled by total/truncated. It also clarifies that figures are estimates finalized by the contract.

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 core purpose and routing alternatives are front-loaded, and no output schema exists so the detailed return-field explanation is largely justified. However, it is delivered as one dense run-on block with some repeated coverage of promo/first-loan flags, which hurts scannability.

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, the description carries the full burden and does so: it enumerates the calculation fields (repayment_total_uah, overpayment_uah, early_repayment, upper_bound, promo_applied, promo_condition), the example fallback (5000/30 with is_example), and the null semantics of first_loan_zero_percent. Nothing an agent needs to interpret the response 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 coverage is 100%, so the baseline is 3, but the description adds semantics the schema lacks: unknown region yields an error response, and limit truncation is surfaced via total/truncated. It also ties amount/term_days to how calculation is computed, though much of this overlaps the per-parameter descriptions.

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 opening states a specific action and scope: it selects МФО whose first-credit tariff satisfies a desired amount/term and computes a repayment figure. It explicitly distinguishes itself from siblings (list_mfo for the full unfiltered list, get_mfo for one МФО, get_city for a region/city page), so an agent can route without opening any 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 gives concrete trigger examples ('де взяти 5000 грн на 30 днів', 'кредит 3000 грн у Львові') and names the alternative tool plus the condition that selects it for each sibling. It also states that filters are independent and combine with AND, and that no filters returns the whole catalog.

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