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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds real value beyond them: it discloses the return payload (each test, the binding constraint, payment, MIP) and that an omitted note_rate falls back to a 12-month median of HUD-endorsed 223(f) loans — a realized history, not a quote. It also warns the result is an estimate, not a commitment. Minor gap: no mention of rounding/tolerance or what happens with incomplete unit_mix.

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 computation, followed by payload, fallback behavior, and the estimate caveat. Dense parenthetical enumeration of thresholds is information-bearing rather than filler, though the first sentence is long enough to slow parsing.

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 an 11-parameter, nested-object tool with no output schema, the description covers the computation, the returned fields, and the note_rate fallback — enough to call it correctly. Residual gaps are the unexplained high_cost_pct and term_years semantics.

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?

With 55% schema coverage the description does add meaning the schema lacks — category drives the LTV (87/90/90+) and DSCR (1.15/1.11) thresholds, purpose drives the cost-to-refinance/cash-out cap, and note_rate's default source is explained. But it says nothing about high_cost_pct (270–405), term_years, elevator, or requested, leaving several parameters undocumented in both places.

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 specific verb (Estimate) and resource (maximum 223(f) proceeds) and spells out the exact computation — lowest of LTV, DSCR, statutory limit, and cost-to-refinance cap. An agent can tell this apart from the sibling statutory_limit (which is only one of the four tests) and from get_loan/program_facts.

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?

Implies usage (sizing a 223(f) loan, an estimate not a commitment) and gives a fallback rule when note_rate is omitted, but never states when to prefer this over statutory_limit or hud_stats, nor prerequisites such as which inputs are mandatory vs optional.

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