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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds real operational context: it discloses the discrete result states (on_peg / depeg_warning / depegged / no_market / unverifiable_fx) and the payment model ($0.03 per call over x402 on Base, prepaid x-credit-token for unlimited use, no free tier, no API key). The cost/auth disclosure is genuinely useful for an agent deciding whether to invoke.

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 core concept (declared peg vs market price) is front-loaded, and the outcome states and payment model follow logically. It is em-dash-heavy and slightly dense, but nearly every sentence carries information an agent needs; minimal waste.

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 single-parameter, output-schema-backed read check, the description supplies everything needed: the concept, the trigger condition, the result taxonomy, and the cost/auth model. With an output schema present it correctly avoids restating return values in detail.

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 100% for the single parameter, so the schema already documents 'address.' The description merely restates the requirement ('Required input: address') without adding format, chain, or validation meaning beyond the schema. Baseline 3 is correct.

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?

Names a specific verb+resource (compare a B20 stablecoin's self-declared currency() against actual DEX market price) and frames it against the sibling verification tools by noting 'the standard verifies nothing' and calling it 'the missing check.' An agent can distinguish it from b20_stablecoin, b20_authenticity, or stablecoin_peg without opening a 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?

Gives a clear trigger — 'Run before settling in any B20 stablecoin' — which tells the agent exactly when this belongs in a workflow. It does not explicitly name an alternative sibling or a when-not condition, so it stops short of full routing guidance.

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