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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so safety is covered. The description adds genuinely new behavior: the credit cost ('Cost: 2 credits') and the fact that the call is keyed on a rate symbol, which the annotations do not convey.

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 short sentences, front-loaded with purpose, with the cost note bracketed at the end — no wasted clauses. Minor redundancy in repeating the title twice ('Benchmark Rate: Benchmark Rate retrieves...'), which is the only real trim available.

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?

For a single-parameter, read-only lookup with an output schema present, the description is essentially complete. Describing the return fields is somewhat redundant given the output schema, and it does not say what happens with an unrecognized symbol, but no critical gap remains.

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% and there is only one parameter, so the baseline is already high. The description still adds value by naming five valid symbols (SOFR, SONIA, ESTR, TONA, SARON) for a field that has no enum, effectively hinting at the accepted value space.

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: 'retrieves current risk-free reference rates', and enumerates the concrete symbols covered (SOFR, SONIA, ESTR, TONA, SARON). That makes the domain unambiguous, though it never distinguishes itself from adjacent siblings such as InterestRate, TreasuryYields, or CurrencyRate.

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 only implied via the phrase 'risk-free reference rates', which hints at benchmark-rate use cases. There is no explicit when-to-use/when-not guidance and no pointer to an alternative sibling (e.g., InterestRate or TreasuryYields) when a different rate family is needed.

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