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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), and the description adds real domain behavior: results change at the July 1, 2026 statutory boundary, proration applies to less-than-full-time enrollment, and an interim exception exists for borrowers enrolled with a loan on June 30, 2026. It stops short of describing the response structure or what happens for dates far outside the stated regimes.

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?

The purpose sentence is front-loaded and the statutory/date specifics follow in one dense block. Density is justified by the reference nature of the data, though the trailing undergraduate-limits sentence is closer to output preview than invocation guidance.

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?

Two optional parameters, no output schema, and the description supplies all the substantive framing an agent needs: what is returned (annual and aggregate caps per borrower type), the effective-date regimes, proration, and the interim exception. There is no output schema, yet the enumerated amounts effectively preview the return content.

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 100%, so baseline is 3; the description goes beyond it by explaining why 'date' matters (the pre/post July 1, 2026 regime split) and by giving substance to each borrower_type value (dependent vs independent undergraduate ranges, graduate, professional, Parent PLUS per dependent student). It does not clarify the 'all' enum value or the today-default behavior beyond what the schema says.

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?

Opens with a precise verb+resource+scope: 'Returns federal Direct Loan borrowing limits in force on a date.' The resource (loan limits) is unmistakably distinct from the repayment-plan siblings (transition dates, RAP payment, RAP vs standard), so an agent can route without opening the 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?

Usage is implied by the date-scoped framing ('in force on a date'), which signals this is a point-in-time lookup, but the description never states when to prefer it or what to do instead when a question is about repayment rather than limits. No explicit when-not or alternative routing is given.

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