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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds real value beyond that: the calculation basis, the rent-cap formula, the effective date, and the unpaged-vs-paged fallback behavior when no county/area is supplied.

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?

A single dense sentence that front-loads the fiscal year and the core resource before the qualifiers, with no filler. It is long but every clause carries information; it could be split for readability but nothing is wasted.

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 still conveys what data comes back (limits per household size, per-unit rent cap, project-average cap) and how paging works. Combined with full schema coverage and comprehensive annotations, an agent has enough to call it correctly.

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 every parameter is already documented in the input schema, which sets the baseline at 3. The description only marginally extends this by framing the rent caps as dependent on household size and tying county matching to the OMB 2023 delineation, but it adds no new format or constraint details.

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 resource (FY2026 USDA Section 538 income limits), the exact basis (115% of AMI, 1-8 persons, effective July 13, 2026), and what else comes back (per-unit rent cap and approximate project-average cap). This clearly separates it from siblings like size_538_loan, list_538_loans, and get_538_lender_table.

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 trailing clause 'Without county or area, lists every area in the state, paged' tells the agent what happens when the optional locators are omitted, which is useful. However, there is no explicit when-to-use guidance, no mention of prerequisites, and no routing to or away from the sibling tools that also deal with 538 data.

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