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

Annotations already mark the tool as read-only, idempotent, and non-destructive. The description adds value by detailing the output (APR rates, recommended actions, lender comparisons) beyond the annotations, though it does not mention rate limits or authentication needs.

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?

Two sentences deliver the core purpose and filter capabilities without redundancy. Every word contributes to clarity, making it efficient for an AI agent to parse.

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?

Given the presence of an output schema, annotations, and full schema coverage, the description adequately covers the tool's functionality. It explains what is returned and the available filters, leaving no critical gaps for a read-only operation.

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% with each parameter described. The description reiterates the filter parameters without adding new semantics (e.g., specific CLTV thresholds or valid state codes). Per guidelines, baseline is 3 when schema coverage is high and no extra meaning is added.

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?

The description clearly states the tool gets a HELOC rate decision, specifies the resource (Home Equity Line of Credit), and lists the returned data (APR rates, recommended actions, lender comparisons). It distinguishes itself from sibling tools like rateapi.lending.auto by focusing on HELOC exclusively.

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 description implies usage for HELOC rate queries but does not explicitly state when to use this tool vs alternatives (e.g., rateapi.lending.mortgage). No exclusions or when-not-to-use guidance is provided, leaving the agent to infer from the tool name.

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