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

With no annotations provided, the description carries the full burden. It discloses the data source (FRED), a 5-minute cache, and precisely what the tool returns: yields across tenors, a parked-yield example on $10k principal, and curated ETF references with expense ratios and use-cases. This is solid behavioral disclosure for a read-only data fetch.

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 dense but every sentence adds value: it front-loads the core purpose, provides a concrete use-case example, enumerates the return payload, and ends with source and cache details. No filler or redundant phrasing.

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 no-parameter tool without an output schema, the description covers all essential information: why to use it, when to use it, what data comes back, and data provenance. It is fully self-contained for invocation.

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?

The tool has zero parameters and an empty schema, so there are no parameter specifics to explain. The description instead clarifies the output structure and contents, which is appropriate. Baseline for 0-param tools is 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 identifies the tool as providing current US T-bill yields and a parked-cash quick-reference for capital-allocation comparisons. It explicitly distinguishes the tool's niche (risk-free vs risky return comparison) with a concrete usage quote, setting it apart from sibling yield-curve 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?

It gives explicit guidance: 'Use this for capital-allocation responses' and explains the comparative reasoning needed. However, it does not name alternative tools or state when not to use it, so it falls just 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.