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

Annotations only establish read-only/open-world, but the description adds the crucial operational fact that each call costs $0.005 USDC via x402 — the equivalent of a rate-limit/cost disclosure. Because there is no output schema, the description also carries the return-content burden and does so by naming the exact fields and derived values returned.

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?

It is front-loaded with the payload content, and every enumerated item is a genuine returned field rather than filler. The single long enumerated sentence and appended cost sentence are dense but not padded, though the list could be marginally tightened.

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 no params, no output schema, and minimal annotations, the description fully covers what is returned and what it costs, which is what an agent needs to call it correctly. It does not state the response format or update cadence, but for a no-argument snapshot tool this is nearly complete.

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 takes zero parameters and schema coverage is 100%, so there is nothing the description needs to disambiguate. The baseline for a parameterless tool is 4; no additional parameter meaning is possible or required.

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 exhaustively enumerates the exact resource returned (fed funds, SOFR, prime, 3-month bill, 2/10/30-year yields, 10y-2y and 10y-3m spreads, MoM/YoY changes, inversion flag), so an agent knows precisely what this tool produces. That itemized scope effectively separates it from broad macro siblings like macro_us or fred_series, which do not promise a bundled current US rate snapshot.

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 word 'now' implies a current-snapshot use case versus historical series tools such as fred_series or macro_us, but no alternative is named and there are no stated exclusions. Usage is inferable from the content list rather than stated, which is the definition of implied guidance.

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