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

Beyond the annotations (readOnly/idempotent/non-destructive/openWorld), the description adds genuinely non-obvious behavior: the call is metered at $0.08 USDC per invocation, and payment credentials must arrive in MCP request headers (X-Payment / X-Payment-Tx / Bearer fg_…) rather than as parameters. It also mentions documented data-boundary caveats in the payload. It stops short of describing failure or insufficient-credit behavior.

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 key payload and pricing/payment facts are front-loaded, which is good. However, the body is fully duplicated in Chinese and English (header blurb, paid-per-call line, and args line appear twice), so a meaningful share of the text is redundant restatement rather than added information.

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?

There is no output schema, and the description does name the returned fields and the payment/auth mechanics, which covers the biggest gaps. What it omits is the semantics of the two optional, null-defaulted filters and any indication of coverage (which stablecoins, which chains), so an agent cannot confidently construct a scoped call.

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%, so the description must carry parameter meaning — but it only restates the names "symbols, ids" with no format, delimiter, expected value shape, or interaction between the two filters. Both parameters also default to null, and the description does not say what happens when neither is supplied.

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 concrete question it answers ("which stablecoin is off its peg") and enumerates the returned fields — price, deviation bps, 24h change, threshold tiers — so the resource is unambiguous. It does not, however, contrast itself with the sibling `stablecoin-peg.now`, leaving the reader to infer that "full" means a richer payload than the snapshot.

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 only implied: the framing question and the word "full" suggest this is the detailed variant to pick when a snapshot is insufficient, but there is no explicit when-to-use, when-not, or named alternative (e.g. `stablecoin-peg.now`). An agent must infer the routing decision from the adjective alone.

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