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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds that the call is free and that a required-sender rule governs payment, plus the pre-payment verification flow — useful context beyond annotations. It does not describe the shape or scope of the returned plan data, so it stops short of rich behavioral disclosure.

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?

Three short sentences with no filler, and the when-to-use directive is front-loaded near the top. The first sentence is a dense comma-list of nouns rather than a readable statement of purpose, which slightly hurts scanability.

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 one-parameter, read-only info tool with no output schema, the description covers what is returned, that it is free, the required-sender constraint, and the verification step to take before paying. An agent has enough to call it correctly and knows the next action, though the return shape remains unstated.

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 coverage is 100% and the schema already documents product as "agent" (default) or "merchant". The description restates "Optional product=agent|merchant" without adding defaults, effects, or selection criteria beyond what the schema provides, so the baseline of 3 applies.

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 enumerates the data the tool surfaces (plan options, USDC subscription wallet, per-plan limits, annual prices, required-sender rule), which implies a read of payment/plan configuration, but it never states a verb+resource plainly. The leading "Free:" is ambiguous — it could mean the call is free of charge or that free-tier plans are returned. An agent can roughly infer the tool's domain but not cleanly separate it from get_platform_info or get_token_balance.

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?

"Prefer this before paying" gives an explicit trigger for when to call it, and the follow-up step (verify with the verify_payment action) tells the agent what to do next. There is no when-not guidance and the verification target is described as an HTTP path rather than a sibling tool, so routing still requires some interpretation.

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