calculate_refinance_break_even

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

No annotations are provided, so the description carries the full burden. It usefully discloses the computed outputs (break-even timeline, interest savings, recommendation), which signals a pure non-mutating calculation. However, it never states key behavioral assumptions that materially affect results, such as whether closing costs are paid upfront or financed, or how the new term extending the loan life is handled.

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 purpose sentence followed by compact Args/Returns blocks; every line carries information and nothing is padded. The Args list largely mirrors the schema parameter names, but the added units justify the space.

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 six required parameters, no annotations, and an output schema present, the description covers inputs, computation, and return shape well enough to call the tool correctly. The remaining gaps are modeling assumptions and edge-case behavior rather than anything that blocks correct invocation.

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 description coverage is 0%, so the description must compensate, and it does: all six parameters are documented with units and meaning ('annual rate as a percentage', 'in dollars', 'remaining_months' vs 'new_term_years' in years). The percent-vs-decimal distinction is especially valuable. It lacks any constraint notes (e.g., non-negative rates), keeping it from a 5.

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 sentence states a specific verb and resource ('Analyse whether refinancing a mortgage makes financial sense') and enumerates exactly what is computed: monthly savings, break-even month, and net interest impact. This is far more than a restatement of the name. It does not, however, explicitly distinguish itself from the overlapping sibling compare_loan_scenarios, so it stops short of a 5.

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?

Usage is implied by the topic (refinance analysis) but there is no explicit when-to-use/when-not-to-use guidance and no routing to alternatives. An agent must infer whether this or compare_loan_scenarios is appropriate for a given refinance question. Adequate but with a clear gap.

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