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

Annotations already indicate read-only, idempotent, non-destructive behavior. The description adds meaningful context by clarifying that values are 'historical observations, not a forecast, recommendation, or real-time quote' and that the pack is 'provenance-backed' — important for interpreting data freshness and reliability. No contradictions with annotations.

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 sentences with no filler. The main action is stated first, followed by concrete use cases and a succinct caveat. Every word earns its place.

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 tool with only 2 optional parameters and no output schema, the description sufficiently conveys the pack's contents, applicable use cases, and key data caveat. It does not explain whether any default date or latest-point behavior applies, but the overall intent and boundaries are clear enough.

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%, so both parameters (date, response_format) are fully documented in the schema. The description adds no additional parameter-level detail, such as how the optional date affects the 'latest' default or how response_format changes output structure. Baseline 3 is appropriate.

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 uses a specific verb 'Combine' with concrete resources — H.15 policy/reference rates, nominal Treasury curve, and 10y-2y/10y-3m spreads — making the tool's aggregation purpose unmistakable. It also clearly implies this is a composite evidence pack versus granular sibling tools like fed_board_h15_rate_history or yield_curve, even without naming them.

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?

Explicit use cases are given: 'summarize the current rate environment', 'build a Federal Reserve rates evidence pack', or use as a direct-Board macro leg. However, there is no explicit when-not-to-use guidance or stated alternative to federated granular tools, so it falls short of a 5.

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