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

Annotations already cover read-only, idempotent, open-world and non-destructive, so the description focuses on adding genuinely new context: a free tier with a daily per-caller quota, and the critical operational detail that payment headers (X-Payment, bearer token) belong in HTTP headers rather than parameters. The only gap is that it does not say what happens when the free quota is exhausted or what the response shape looks like.

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?

The English summary is front-loaded and earns its place, but the full Chinese and English restatements duplicate the same facts rather than adding new ones, and the payment-header note is buried at the end. It is serviceable but padded.

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 and an undocumented parameter, the description carries a heavy burden; it partially meets it by describing the return content and the payment/auth mechanics, but leaves the symbols format, default behavior and quota-exhaustion handling unexplained. Adequate but visibly incomplete for a self-described free, quota-limited endpoint.

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 0% for the single 'symbols' parameter, and the description only restates its name ("Args: symbols") without saying whether it accepts a comma-separated list, an array, or which symbol format is expected. It also does not explain the null default, which presumably means all stablecoins, so the gap left by the bare schema is not filled.

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 states a concrete question it answers ("which stablecoin is off its peg") and names the output content — depegged and slightly off coins plus worst deviation in bps. It distinguishes itself implicitly as a summary view, though it never names the sibling peg_detail as the drill-down alternative.

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?

Usage is implied by the framing question and the note that it is free, suggesting a quick default check, but there is no explicit when-to-use versus peg_detail or when-not guidance. The agent has to infer the summary-versus-detail split from sibling names alone, which the definition does not address.

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