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

The description adds valuable behavioral context beyond the annotations (readOnlyHint=false, destructiveHint=false): it states the tool returns a checkout_url, that credits land automatically after payment, and that it requires specific auth and plan. It also mentions the enrollment binding, enriching the agent's understanding of side effects and constraints.

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?

Four sentences, each carrying distinct information: purpose, parameter, return/behavior, and auth/alternative/enrollment. No filler or repetition, and the most critical action is front-loaded. Perfectly sized for the tool's complexity.

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 only one parameter and no output schema, this description covers all necessary aspects: what the tool does, how to use the parameter, what is returned, what happens after payment, required scope/plan, and an exclusion for free trials. It is fully self-contained for an agent to select and invoke it correctly.

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 schema already provides 100% coverage with the enum and description for pack_id. The description repeats the enum values and adds a small detail ('The founder sees the price on the checkout page'), which is minor incremental value. This matches the baseline for high schema coverage.

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 it creates a credit top-up checkout link for the current product run, using the specific verb 'Create' and resource 'credit top-up checkout link'. It distinguishes from sibling create_checkout by explicitly mentioning 'on a free trial use create_checkout first', and adds scope with 'THIS product run' and 'Always bound to your own enrollment'.

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?

Explicit guidance is given on when to use this tool versus create_checkout: 'Requires the "act" scope and the Founder plan (on a free trial use create_checkout first)'. This provides clear conditions and names the alternative tool, which is exactly what effective usage guidelines need.

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