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 still adds real context beyond them by clarifying these are advertised (not quoted) rates and that each scenario carries the existing first-mortgage balance and implied CLTV.

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?

Dense but front-loaded: the resource and data scope come first, then the caveat and the routing pointer. No filler sentences, though the second sentence is clause-heavy.

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 params and no output schema, the description does the necessary work by describing what the returned scenarios contain and where to go for personalized offers. It is complete for a zero-argument read tool, missing only explicit detail on refresh cadence.

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 baseline is 4; there is nothing further for the description to disambiguate.

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 verb+resource ('Today's As Low As rates for a HELOC and a home equity loan') and explicitly ties itself to the sibling get_mortgage_rates by revision, so an agent can separate the two rate tools without opening either 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?

Gives a clear when-not ('Advertised rates, not a quote') plus the exact alternative for personalized results ('call get_start_link'), which is strong routing guidance. It does not explicitly say when to prefer this over get_mortgage_rates beyond the product distinction, so it falls just short of the top band.

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