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

With no annotations, the description carries the burden of behavioral disclosure. 'Returns' clearly signals a read-only operation, and the description specifies the data window and series. It does not discuss rate limits or auth, but for a zero-parameter data retrieval tool those are less critical; nothing destructive or state-changing is implied.

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 short, dense sentences with no filler. The first sentence names both resources, and the second sentence states output granularity. Every word adds value.

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 zero-parameter read-only tool, the description explains the return content and timeframe. There is no output schema, so the description provides the essential return-value information. A slightly more explicit statement of output format (e.g., date + rate pairs) would be nice but is not necessary for correct 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, so the description does not need to explain parameter semantics. The empty input schema is fully self-describing, and the description adds meaning by defining what the returned data contains. Per the 0-params baseline, this scores 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 uses a specific verb ('Returns') and precisely identifies the resource: DeFi Base Rate (with parenthetical definition) and the 3-month U.S. T-Bill rate. It also states the output scope (~30 daily points). This clearly distinguishes get_rates from siblings like get_hacks, get_vault, and list_vaults.

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 makes clear that this tool is for retrieving recent rate series. It does not explicitly state when not to use it or name alternative tools, but the subject matter is unique among siblings, so an agent can infer this is the go-to tool for rates. There are no exclusion conditions to document.

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