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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), so the description's contribution is the computational behavior: it discloses the exact agency rule sets applied (FHA 31/43 and AUS 46.99/56.99, Conventional 28/36 to 45/50, VA 41, USDA 29/41) and that results are deterministic. That is meaningful added context an agent could not get from the annotations.

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 verb and the primary outputs, with no filler wording. The downside is that it is a single dense mega-sentence whose long list of agency thresholds is hard to parse, but every clause carries substantive information.

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 19-parameter calculator with no output schema, the description never characterizes the returned payload — presumably a structured object with front-end/back-end ratios per agency, per-agency limits, and paydown deltas. An agent cannot anticipate the response shape or which fields map to which computed scenario.

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 100%, so the schema already documents all 19 parameters in detail, including the student-loan plan and agency enums. The description restates the agency imputation concept but adds no syntax, precedence, or interaction rules beyond what the schema says — the baseline 3 is appropriate.

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 ('Computes') plus the concrete artifacts produced: front-end and back-end DTI ratios, agency-specific student loan imputations, maximum allowable monthly debt per agency, and dollar debt reduction. It is clearly distinguishable from siblings like calculate_mortgage_affordability or compare_fha_vs_conventional, which do different jobs.

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 only implied by the enumeration of outputs — an agent can infer 'call this when you need DTI math and agency caps.' There is no explicit when-to-use statement, no exclusions, and no pointer to the related siblings such as simulate_debt_payoff_and_readiness for the lump-sum tradeoff scenario.

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