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

Annotations already declare read-only, idempotent, non-destructive, and closed-world, so the safety profile is covered; the description adds genuinely new behavior: one best quote per institution, health grade and as-of date included, and city mode putting local branches first with up to 3 addresses while filling from the state. It does not mention rate limits, caching, or how "live" rates are refreshed, so it stops 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?

Two dense sentences with the scoping and output shape front-loaded before the key-lookup pointer. Every clause carries information, though the long parenthetical product list is slightly heavy relative to its value.

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 output schema, the description takes on the burden of explaining return values and does so (one quote per institution, health grade, minimum deposit, as-of date, link, local-branch addresses). Combined with the schema for filters, an agent has everything needed to call it correctly.

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 83%, so documented fields already carry the meaning of city, state, min_deposit, and product_key. The description restates the product_key sourcing (list_rate_keys) and product families but adds little beyond the schema, and it never mentions limit or institution_type, so the 3 baseline 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 and resource ("Top live rates ... for one product") and enumerates exactly which rate categories are covered, plus the geographic scoping options (national/state/city). It also clarifies the output shape ("one best quote per institution"), which distinguishes it from the sibling get_average_rates without ambiguity.

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 to list_rate_keys for valid product_key values and gives concrete key examples, plus clear rules for when to supply state, city, or omit both for national. It never states when to prefer a sibling like get_average_rates or get_mortgage_lenders instead, so the alternatives half of the guidance is missing.

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