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

Annotations already declare readOnlyHint and idempotentHint, so safety is covered. The description adds a genuinely useful behavioral rule not in the annotations or schema enum: $0 entitlement is treated as full entitlement with no county cap, which changes how the caller should interpret inputs. The trailing 'Read-only' merely repeats the annotation.

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?

One dense sentence front-loads the computation and its outputs, with the edge-case rule second. Nearly every clause earns its place, though the closing 'Read-only' is redundant with the annotation.

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 correctly enumerates what the caller gets back (remaining entitlement, max $0-down loan, down payment), which is exactly the missing piece. Coverage of the $0 edge case and the county cap makes it complete enough to call without ambiguity.

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 67%, with county and entitlementAlreadyInUse documented in the schema itself. The description restates the $0/entitlement rule and ties county to a conforming-limit cap, but adds nothing about purchasePrice syntax or the interaction between the in-use amount and the county limit calculations. 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 computation with three concrete outputs (remaining entitlement, max $0-down loan, and the 25% down payment above that), which is far beyond a tautology. It does not, however, name or contrast itself with the closest sibling, va_purchase_power, so sibling differentiation is left to inference.

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 scope ('For a Hawaii county') implies when the tool applies, but there is no explicit when-to-use guidance and no mention of alternatives such as va_purchase_power or calculate_affordability, even though those siblings overlap in territory. Usage is implied rather than directed.

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