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

With no annotations, the description must disclose behavior fully. It covers cost ($0.99), payment chain (USDC on Arc/Base), minting and delivery to signing wallet, return of agentId and both transactions, and the no-charge guarantee. This is strong transparency for a purchase tool, though it omits failure modes and reversibility.

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 paragraph that front-loads the purpose and process. It is efficient with no wasted words, though it packs a lot of information that might benefit from splitting into bullet points.

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?

The description explains the two-step process, the return value (agentId and both transactions), and the no-charge policy. However, it does not cover error handling, what happens if payment is invalid, or detailed parameter guidance. For a tool with 5 parameters and no output schema, this is a moderate gap.

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 only 20% (only 'payment' has a description). The description explains 'payment' semantics and the two-step flow, but does not provide guidance for the required 'name' and 'description' parameters or optional 'image' and 'services'. Given low 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 states the action (buy ERC-8004 identity) with a specific method (signature alone) and distinguishes it from sibling tools like arc_passport_draft and arc_passport_status by focusing on the purchase and completion flow. It leaves no ambiguity about the tool's primary function.

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?

Provides explicit step-by-step usage: call without 'payment' to get terms, sign them, call again with 'payment'. Also notes that refused inputs are never charged, which helps the agent decide when to invoke. Does not explicitly compare to alternatives, but the usage is clear.

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