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

With no annotations provided, the description carries the full burden of behavioral disclosure. It unambiguously states the operation is PAID, involves a $0.01 USDC payment to Merchant, that Treasury pays upstream, and that failover on errors occurs. These are important non-obvious behaviors that an agent must know. It could go slightly further by describing return behavior or side effects beyond payment, but the key traits are disclosed.

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 three sentences with zero wasted words. The core action and cost implication are front-loaded in the first sentence, usage guidance in the second, and tier clarification in the third. Each sentence earns its place and the structure makes the tool's purpose immediately scannable.

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 paid, routing, multi-parameter tool with no output schema, the description covers the essential context: payment, auto-picking, failover, tier semantics, and budget implications. It also names sibling tools for boundary conditions. The minor gap is that it does not describe the shape of the returned result or how the agent should interpret the upstream API's response, which is relevant for a tool with no output schema.

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%, so the baseline is 3. The schema already documents all six parameters, including tier enum values and max_attempts defaults. The description restates tier semantics ('economy=cheapest; verified=reliability-scored') but mostly duplicates schema information. It adds no substantial new meaning beyond what the input schema already provides.

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 opens with a specific verb and resource: 'PAID inbound $0.01 USDC to Merchant, then auto-pick and call the best Base x402 API for a natural-language task.' It clearly differentiates from siblings by explicitly naming call_x402_api and quote_route as alternatives to prefer over or not prefer. This is a clear, non-tautological purpose statement.

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 explicitly states when to use this tool: 'Prefer over call_x402_api when you have a task but no specific tool_name/URL' and 'Prefer over quote_route when you want data now, not a dry-run ranking.' It also explains the tier choice semantics ('economy=cheapest; verified=reliability-scored'), giving clear selection guidance.

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