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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior. The description adds meaningful behavioral context beyond annotations by disclosing the monetary cost per call and the x402 payment mechanism, which is critical for an agent deciding whether to invoke a paid tool. It does not mention rate limits or data freshness, but the cost disclosure is valuable.

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 two short sentences with no filler. The core subject is front-loaded, and the cost/payment detail is placed second. Every word earns its place, and the title's '(paid)' marker is reinforced without being redundantly expanded.

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 simple tool with one optional parameter and rich annotations, the description covers the main output themes and the paid nature of the call. However, it omits any explanation of the 'limit' parameter and does not describe the response format, which would be more important given there is no output schema. It is adequate but has clear gaps.

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?

The schema has one optional 'limit' parameter with min/max constraints but no description, and the tool description provides zero coverage of parameter semantics. The property name and constraints hint at result limiting, but the description does not clarify what the limit applies to or how it affects the response. With 0% schema description coverage, the description should compensate but does not.

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 clearly identifies the resource: circulating USD-pegged stablecoin supply, and adds specific output dimensions (peg mechanism, chain count). It distinguishes itself from generic supply tools like chain_supply_at by focusing on stablecoin-specific aggregate data. It lacks an explicit verb like 'get' or 'list', but the meaning is unambiguous.

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?

The description implies usage for stablecoin supply queries and provides a practical prerequisite by stating the $0.001 USDC cost via x402. However, it does not explicitly state when to prefer this tool over alternatives or when not to use it. The usage context is implied rather than explicit.

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