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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds a legacy status, the output type (credit bundles + buy URLs), and the caveat 'not the authorize standard' — all useful beyond the structured annotations. However, terms like 'volume validates' and 'x402' are not fully explained, so it falls short of a 5.

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 that packs legacy status, differentiation, and output details. It is not overly long, but the heavy use of abbreviations and jargon makes it less immediately parseable. Still, every clause earns its place and it is reasonably structured.

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 tool has no required parameters, a rich annotation set, and an output schema, the description provides enough context for basic invocation. It clarifies the relationship to sibling tools and the legacy nature. Minor gaps like the meaning of 'volume validates' and 'authorize standard' prevent a perfect score, but it is largely complete.

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 tool has zero parameters, so there is no parameter behavior to clarify. The schema coverage is 100% (trivially), and the description adds context about the output. With no parameters, a baseline of 4 is appropriate.

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 uses a clear verb ('Returns') and specifies the resource ('credit bundles + x402 buy URLs') and scope ('volume validates only'). It also distinguishes itself from siblings by explicitly positioning as 'LEGACY' and 'not the authorize standard,' which prevents confusion with similar tools.

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 explicitly instructs the agent to prefer alternative tools ('Prefer sqlguard_handshake then sqlguard_challenge'), and labels the tool as 'LEGACY prepaid catalog (OFF TABLE as wealth/primary)' which strongly signals it should not be used as a primary option. This provides clear when-to-use and when-not-to-use guidance.

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