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

Annotations already declare readOnlyHint and idempotentHint, so the description adds value by explaining the peg deviation measurement methodology (against peg using DefiLlama's price) and noting the data is free. This gives useful context beyond the safe read-only hint.

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 description is front-loaded with the core data points in the first sentence, then adds source, filtering, and measurement details. No fluff; every sentence adds information about what the tool does or returns.

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?

Given no output schema, the description lists the expected data fields (supply, supply changes, price, peg deviation) and mentions filtering, which sets clear expectations. It omits details like pagination or sorting, but these are likely minor for this use case.

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 only 33%, so the description's 'Filter by symbol or peg type' compensates by clarifying the intent of two parameters. The limit parameter is self-explanatory. The description also mentions peg_deviation_pct, which appears in the output, helping agents understand the tool's response.

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 'Every stablecoin's circulating supply, 1 d/7 d/30 d supply change, current price and peg deviation' — a specific resource and data set. The mention of 'spot depegs and mint/burn flows' differentiates it from sibling price tools like crypto_price or price_history.

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?

While it doesn't explicitly name alternatives, it provides clear context by describing filterable dimensions (symbol, peg type) and concrete use cases (spotting depegs, mint/burn flows). This is enough for an agent to recognize when to delegate to this tool over generic price or chain TVL tools.

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