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

With no annotations at all, the description carries the full burden and does disclose the notable behavioral trait: this is a paid call at $0.005 USDC via x402 on Base. It also states the responsive content and units (bp). It stops short of covering data freshness, rate limits, or response shape, which matters for a paid call.

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 sentences, zero filler. The analytical content is front-loaded and the commercial term (price/payment rail) is placed last where it can be skipped by an agent that already knows the pricing model.

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?

No output schema and no parameters, so the description must enumerate returns — which it does precisely (slopes, inversion flags, three named 10Y spreads, units). Missing only freshness/as-of semantics and the response envelope, which is a minor gap for a zero-arg tool.

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?

Zero parameters with additionalProperties false, so there is nothing for the description to disambiguate. Baseline 4 applies; the description correctly avoids inventing parameter details.

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?

Names the exact quantities computed (2s10s and 3m10y slopes in bp, inversion flags) and the exact cross-market 10Y spreads, over named regions. It is specific enough to distinguish from a raw curve-level tool, but it never names yields_curve or yields_rate, so sibling differentiation relies on the agent inferring 'spread' vs 'level'.

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?

No explicit when-to-use or when-not-to-use statement, and no mention of the sibling tools yields_curve/yields_rate. Usage is only implied by the enumerated outputs — an agent can infer this is the tool for spread/slope questions rather than outright yields, but nothing confirms that routing.

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