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

Annotations already cover readOnly/idempotent/non-destructive/closed-world, so the bar is lower. The description nonetheless adds meaningful context beyond structured fields: the exact denominator definition (actions 1,2,3; loan_type 2; reverse mortgages excluded), the warning that commonly published 13.6% figures are a different universe, and the 'not a prediction' caveat. It stops short of detailing response shape or correction specifics, but it is well above the annotation baseline.

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 answering questions and the NOT FOR routing before the provenance tail, so an agent can decide quickly. It is somewhat long (the inline figures and attribution could be trimmed), but nearly every sentence carries routing or quoting value.

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 no-parameter static lookup with no output schema, the description supplies the returned figure, its universe, provenance, and the quoting caveat — everything an agent needs to use the result correctly without a return-value schema.

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?

Zero parameters, so the schema imposes no burden and the baseline is 4. The description correctly avoids inventing parameter detail and instead scopes the tool's fixed universe.

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 exactly what it returns — the national 2025 FHA denial rate with its universe — and explicitly differentiates from siblings by excluding state/lender/metro breakdowns and pointing to 'the dedicated tools'. An agent can distinguish this from get_state_denial_stats or get_lender_denial_stats 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?

Opens with a concrete 'ANSWERS' list of natural-language questions, then a 'NOT FOR' list naming the excluded universes (conventional/VA/USDA, purchase-only, other years, state/lender/metro) and where to go instead. Both when-to-use and when-not-to-use are explicit.

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