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

With no annotations, the description must carry the transparency burden. It explains the legal meaning of arrhes (buyer forfeits, seller returns double) but says nothing about the tool's side effects, mutability, or whether it is read-only. The payment example hints at a transaction but does not clarify state changes.

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 a single dense sentence, not overly long, but it packs in legal references, distinctions, and a payment example. It is concise but sacrifices clarity for brevity.

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?

Given the open schema and lack of annotations, the description is the only context. It explains the concept and a required parameter, but it fails to specify what the tool returns, how it executes, or its exact role among the many sibling tools. The example payment is not contextualized sufficiently.

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 description explicitly mentions 'Requires amount_eur', which is a parameter requirement, but the schema itself only has additionalProperties: true with no defined properties. The 'Paid $0.01 USDC Base x402' part is unclear—it could be an example value or a different parameter. Other potential parameters are not explained.

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 defines the legal concept of arrhes and distinguishes it from acompte, but it does not state the tool's actual action (e.g., create, calculate, process). It is cryptic with 'Paid $0.01 USDC Base x402' suggesting a payment example, yet the core function remains ambiguous.

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 mentions 'distinct from acompte' which provides a contrast, but offers no explicit guidance on when to use this tool versus the acompte tool. The requirement for amount_eur is a prerequisite, not usage direction.

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