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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), so the description's job is to add context — and it does: data provenance (freerateupdate.com publications), freshness ('Today's'), one rate per product, and the key semantic caveat that these are advertised rates rather than quotes. It does not mention pagination, rate limits, or caching, which keeps it short of a 5.

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 core content ('Today's As Low As rates from FreeRateUpdate') is front-loaded and the actionable routing to get_start_link comes last in a short closing sentence. The middle sentence is dense and lists products and return fields in a long clause, but each element is informative rather than filler.

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?

There is no output schema, so the description must describe return contents — and it does: per-product rates with example scenario (state, ZIP, value, loan amount, credit score), points, fees and APR. Combined with the quoted-vs-advertised caveat and the sibling pointer, an agent has everything needed to call it and interpret results.

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?

The single 'purpose' parameter has 100% schema description coverage with an explicit enum, so the schema already carries the meaning. The description hints at product scope but never explains that 'purpose' filters by loan purpose, so it adds nothing concrete beyond the schema — baseline 3.

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 states a specific verb and resource (today's advertised mortgage/HELOC rates) and enumerates the covered products, so an agent knows exactly what it returns. It also names a sibling (get_start_link) as the different route for personalized offers, which pins it apart from get_network_rate_summary and get_start_link.

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?

It gives an explicit when-not ('These are advertised rates, not a quote') and names the alternative to use instead ('to get the person their own offers, call get_start_link'). No inference is required to route correctly between this tool and get_start_link.

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