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

Annotations already cover the safety profile (readOnlyHint true, openWorldHint true), so the bar is lower. The description adds genuinely useful behavioral context beyond the annotations: a per-call cost of $0.003 USDC via x402, which materially affects an agent's decision to call it. It does not, however, cover pagination, data freshness, or limit 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?

A single dense sentence that front-loads the resource and data fields before the filters and the cost note. Every clause carries information, though the packed enumeration makes it slightly heavy to parse at a glance.

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, the description usefully enumerates the returned fields, which is exactly what's needed for this tool. It still omits limit semantics and default behaviors, which matters given the low schema coverage and three parameters.

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% (only 'chain' is described). The description compensates for the undocumented 'symbol' parameter by stating filtering is by symbol or chain, but the 'limit' parameter is unexplained in both the schema and the description, leaving a real gap.

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 names the exact resource (stablecoin market) and enumerates the specific fields returned: circulating supply, price, depeg percent, 1-day and 30-day supply change, plus an off-peg list. This is far more precise than sibling tools like crypto_price or token_price, and an agent can tell what data it will get without opening the schema.

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?

It states the available filters ('filterable by symbol or chain') and that off-peg coins are included, which implies when to reach for it, but gives no explicit when-not or named alternatives (e.g., crypto_price for a general price, token_scan for on-chain security). Usage is inferable rather than directed.

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