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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds valuable context: it returns a markdown table, covers up to 10 years of daily history, and lists the specific data series. It does not contradict the annotations and enriches the behavioral understanding beyond the structured hints.

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 three sentences: the first defines the output, the second gives use cases, and the third distinguishes from the sibling. Every sentence serves a purpose, and the most critical information (what it returns) is front-loaded. It is slightly longer than minimal but remains efficient and well-organized.

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 an output schema present, the description need not detail return values. It covers the data series included, the time range, the use cases, and the sibling distinction. All necessary information for an agent to correctly invoke this tool—including the single parameter's meaning via schema—is present. Nothing critical is missing.

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 the parameter 'days' is described in the schema as 'Number of days of history (default 30)' with a maximum of 3650. The tool description mentions 'Covers up to 10 years of daily history,' which aligns with the max but adds little beyond what the schema already states. There is no added syntax or formatting guidance, so it stays at the baseline for high schema coverage.

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 opens with a precise verb and resource: 'Get daily U.S. policy and money-market interest rates' and enumerates exactly which rates are included (Effective Fed Funds, SOFR, Prime, Treasury yields). It also differentiates from the sibling get_treasury_yields by explicitly stating it covers only selected maturities and directs the agent to the sibling for the full curve. This leaves no ambiguity about the tool's scope.

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 states when to use the tool: for monetary-policy questions like 'Where is the Fed funds rate now?' or for inversion analysis comparing policy rates to long-end yields. It also names the alternative tool get_treasury_yields and the condition under which to use it ('For the full Treasury curve across all maturities'). This is clear and actionable guidance.

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