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

Annotations already declare the safe read-only profile, yet the description adds real context beyond them: no order exists, nothing is charged until sign-in, terms acceptance and Stripe payment, the agent never sees card details, the returned price is informational only, and the caller cannot set prices or accept terms.

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 purpose is front-loaded in the first clause, and the follow-on sentences each carry distinct behavioral information (no charge yet, no card details, informational price, VA-only). It is on the verbose side, with the read-only point partially duplicating the annotations, but nothing is truly wasted.

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?

With no output schema, the description still tells the agent what comes back (a checkout link and an informational price) and what the flow requires (sign-in, terms acceptance, payment on Stripe). Combined with the annotations, an agent has everything needed to call and interpret this tool.

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 schema already documents productCode, billingPeriod and countryCode including the enum values and default. The description only echoes the 'one package and one billing period' pairing and adds no format or sourcing detail beyond what the schema provides; baseline 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?

States a specific verb and resource ('Returns the checkout page link') and pins the scope to exactly one package and one billing period, which cleanly separates it from get_package and list_packages even without naming them.

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 gives a clear situation for use ('so the person can finish and pay themselves') and states important exclusions: packages are for virtual assistants, other accounts are blocked at checkout. It stops short of naming an alternative tool to use when the caller wants order details or package data.

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