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

Annotations already declare readOnly, idempotent, non-destructive, and openWorld, so the safety profile is covered. The description adds genuinely new behavioral context: the data source (FRED) and the cost model ($0.02 USDC per call via x402 on Base or Solana), which an agent needs before invoking. It does not specify the response shape (scalar vs. object with interpretation text).

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 tight sentences plus a price line, front-loaded with what is returned and followed by the interpretive baseline, source, and cost. Every sentence carries distinct information with no redundancy.

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 output schema, the description carries the burden of describing the return, and it does so at a high level (spread plus policy-stance interpretation). Combined with source and per-call pricing, an agent has enough to decide and call, though the exact return structure is left unspecified.

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, so the baseline is 4; there is nothing for the description to disambiguate. It correctly spends its words on output meaning and pricing instead of restating a nonexistent input schema.

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 names a precise verb and resource — the spread between EFFR and IORB — and even defines both acronyms, so an agent can tell it apart from siblings like get_yield_curve, get_series, or get_recession_indicator without opening a schema. It stops short of explicitly contrasting itself with any sibling, which keeps it out of the top band.

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 phrase 'with an interpretation of Fed policy stance' implies the use case (assessing policy posture) and the note that 'EFFR below IORB is the normal operating band' hints at how to read the result. But there is no explicit when-to-use, when-not-to-use, or named alternative such as get_series or get_yield_curve, so usage must be inferred.

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