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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuine context beyond that: data coverage begins 2026-06-12 and asOf resolves to the version current on a given date, which materially affects how the agent should call it.

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?

Three sentences, front-loaded with the core verb and scope, then the snapshot rule and the coverage caveat. The middle enumeration of returned fields is a long run-on that could be tightened, but it carries information and no sentence is wasted.

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 usefully enumerates what is returned (rates, tiers, fees, features, eligibility, constraints, source quality flags, dates, lender links) and flags the 2026-06-12 data start. It omits edge behavior such as an asOf before the coverage start or a not-found product, which is a minor gap for a read-only lookup.

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%, so both required ids and asOf are already documented in the schema. The description's gloss on asOf ('returns the version current on that date') largely restates the schema's 'Latest snapshot on or before YYYY-MM-DD' and adds little parameter-level meaning, so the 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?

The description states a specific verb+resource: retrieving exact CDR product-reference detail (every rate entry and tier) for one institution and product. It clearly distinguishes a single-product detail lookup from aggregate/temporal siblings, though it never names a sibling like rate_history or compare_rates explicitly.

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?

Usage is implied by the required institutionId/productId focus and the asOf snapshot semantics, but there is no explicit when-to-use/when-not-to-use guidance and no routing to alternatives such as rate_history or rate_changes. An agent must infer the boundary from the sibling names alone.

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