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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely useful context beyond that: rates are advertised rather than quoted, sourced verbatim from freerateupdate.com, one rate per product, and each carries the scenario it was quoted for. It stops short of describing pagination or freshness guarantees.

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?

Front-loaded with the identity and product list, and closes with the actionable next step. The mid-sentence enumeration of scenario fields (state, ZIP, property value, loan amount, credit score, points, fees, APR, LTV) is dense but each item earns its place by telling the agent what comes back.

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 carries the burden of describing return values — and it does, listing the per-product rate plus the quote scenario, points, fees, APR and LTV. Combined with the advertised-vs-quoted caveat and the routing hint, an agent has everything needed to call and interpret this tool.

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% and the single enum parameter is fully documented in the schema. The description never mentions the purpose filter or what filtering by purchase/refinance/cash_out/heloc/home_equity does to the result set, so it adds no meaning over the schema. Baseline 3 applies.

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 mortgage and home equity rates) and enumerates the exact product set returned (HELOC, home equity loan, cash-out refi, then fixed terms, FHA, VA, jumbo, ARMs). An agent can distinguish this from get_heloc_rates and get_network_rate_summary purely from the description.

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?

Explicitly routes the agent: these are advertised rates, not a quote, and to get the person their own offers you call get_start_link. That is clear when-to-use-next guidance, but it does not say when to prefer the narrower sibling get_heloc_rates over this broad product listing.

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