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

Annotations already declare read-only/idempotent, but the description adds genuinely new behavioral facts: a failed read returns 503 and is not charged, and each call costs 0.02 USDC via x402 with an explicit list of payment chains. Pricing and failure-billing semantics are exactly the kind of context annotations cannot express.

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?

Four short sentences, front-loaded with the usage trigger, then output, then failure behavior, then price. No sentence is redundant against another.

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?

An output schema exists, yet the description still names the key return fields (NAV, yields, contract, method), covers error handling, and discloses payment requirements. Nothing an agent needs to decide or call correctly is missing.

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?

Schema coverage is 100% and the schema itself already lists the five product ids and the omit-for-all behavior. The description adds nothing beyond that on the single parameter, so baseline 3 applies.

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?

States a specific resource (realized 7-day and 30-day yield of tokenized treasury and credit products) plus the computation source (issuer on-chain prices). This clearly separates it from neighboring market-data siblings like get_basis, get_spot, or get_peg_deviation.

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?

"Use when an agent needs the realized 7-day and 30-day yield..." gives an explicit trigger condition. It does not name an alternative tool or state when not to use it, so it stops short of a 5, but the context is unambiguous.

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