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

Annotations already declare readOnly, idempotent, and openWorld, but the description adds genuinely new operational context: the $0.02 USDC-on-Base x402 price and the HTTP 402 failure mode for unpaid calls. That payment/auth behavior is not derivable from the annotations. It stops short of describing the returned payload or any rate limits.

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?

Front-loaded with the core purpose, then input guidance, an example, and the payment terms in tight, telegraphic sentences. Every sentence carries information an agent needs to invoke the tool.

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?

No output schema exists, yet the description never sketches the return shape (scheme name, coverage limits, etc.), which is the main remaining gap. For a simple two-parameter lookup with payment semantics fully covered, it is otherwise complete enough to call correctly.

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% and the schema already lists the allowed country values, the topic default, and examples, so the description's 'US, UK, CA, AU, NZ' and default-topic restatement add little beyond the schema. Baseline 3 is appropriate when the schema carries the parameter documentation.

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 (look up) and resource (deposit-insurance or related scheme) plus a clear scope constraint (English-speaking countries). The sibling tools (health_check, money_fact, pricing_list) are unrelated, so no differentiation is needed and none is missing.

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 tells the agent what to pass (country ISO, optional topic) and what the default topic is, but gives no explicit when-to-use or when-not-to-use guidance. Usage is implied by the lookup framing rather than stated.

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