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

With no annotations, the description carries the full burden and does disclose meaningful behavior: the data is a daily snapshot, it is credited to DefiLlama, an as-of date is returned, and coverage is capped at the top 25. It omits rate limits, pagination/response shape, and what the unparameterized call returns versus the symbol-filtered call.

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?

Two front-loaded sentences: the returned fields come first, followed immediately by usage triggers. Slightly redundant phrasing ('stablecoin supply: total ... circulating supply') costs a little density but nothing is wasted.

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?

For a one-optional-parameter, no-output-schema tool, the description covers what is returned (totals, shares, top 25), the refresh cadence, the data source, and the as-of date. Missing only edge behavior such as unknown-symbol handling or the arbitrary cutoff of top 25.

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% for the single optional 'symbol' parameter, so the schema already documents its meaning ('e.g. USDC'). The description's phrase 'a stablecoin's supply' only lightly reinforces that the symbol narrows results to one coin, adding little beyond the schema baseline.

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 ('get') and resource ('stablecoin supply') and enumerates the exact content: total USD-pegged circulating supply, USDT/USDC share, and top 25 by supply. No sibling tool in the list covers stablecoin supply, so an agent can route here unambiguously.

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 three concrete user-intent triggers ('how big is the stablecoin market', 'USDT vs USDC share', 'a stablecoin's supply'), which clearly frames when to call it. It stops short of naming alternatives or stating when not to use it (e.g., historical time series vs snapshot), so it is clear context but not full routing guidance.

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