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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior. The description adds context about the data richness (percentiles and volume) not present in FRED, and explains default behavior. It doesn't disclose potential latency or rate limits, but given the strong annotation coverage, the added value is sufficient for a 4.

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 description is a single, dense paragraph that front-loads the resource, then explains the two modes, and ends with the differentiation from FRED. Every sentence earns its place, with no fluff or repetition. The structure is logical and scannable.

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 read-only data retrieval tool with no output schema and only two optional parameters, the description covers what data is returned (latest values or history with percentiles/volume), the default behavior, and the key distinction from an alternative. Annotations handle the safety profile. Nothing critical is missing for an agent to call this tool 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 100% with both parameters documented. The description adds semantic value by explaining the interplay between rate_type and number: number only applies when rate_type is not 'all', and it clarifies the default behavior of each mode. This goes beyond the schema's simple field descriptions, warranting a 4.

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 clearly states the resource (reference-rate publications) and enumerates the specific rates included (SOFR, SOFRAI, EFFR, OBFR, TGCR/BGCR). It explicitly differentiates from fred_get_series by noting this tool carries percentiles and traded volume that FRED lacks, so an agent can distinguish it from sibling tools.

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?

The description explicitly explains when to use rate_type=all (latest values of every rate) vs a specific rate_type with number>1 (history with percentiles/volume). It also names fred_get_series as the alternative and the exact condition under which that alternative is insufficient, providing clear routing guidance.

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