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

With annotations present the bar is lower, and the description adds real operational context the annotations do not carry: per-call cost ($0.02), the PAYMENT_REQUIRED failure mode when credit is absent, free sample mode, and the 'confidence none, supply only' behavior for issuers lacking third-party attestation. readOnlyHint=false and idempotentHint=false are consistent with a per-call billed fetch, though destructiveHint=true is left unexplained for a pure data-retrieval tool.

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?

Front-loaded with purpose and return shape, then usage, then billing and sample mode — a sensible ordering. It is a single dense paragraph with some restatement of schema details (period, sample), so it is efficient but not maximally tight.

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, so return-field enumeration is optional and the description spends its words well on payment, sample mode, period default and the unattested-issuer case. It leaves minor unresolved points: the semantics of destructiveHint/non-idempotency and the behavior when neither symbol nor issuer is passed.

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 description coverage is 100%, so issuer, period, sample and symbol are already documented in the schema; the description largely restates them (symbol or issuer, period=YYYY-MM selects an earlier month, sample=true for a free example). It adds no format or precedence rules beyond the schema, and notably does not say what happens when no parameter is supplied even though none are required. Baseline 3 is appropriate.

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 verb+resource: 'Latest parsed reserve attestation for one stablecoin issuer as JSON', then enumerates the payload (as_of, total reserves, composition, attestor, source_url, on-chain supply, reserve ratio). It is unmistakable against the sibling stablecoin_list_issuers, which only lists issuers.

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?

Gives a clear selection condition: 'Use it when an agent needs machine-readable backing data instead of reading the issuer's PDF', plus how to reach an earlier month via period=YYYY-MM and how to get a free trial via sample=true. It stops short of an explicit when-not or naming the sibling as the alternative, so it is contextual rather than exhaustive.

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