billing_list_packs

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

With no annotations, the description carries the behavioral disclosure burden. It states that the tool returns all packs with SKU, USD price, and credit amount, but does not explicitly declare read-only status or discuss error conditions. However, the verb 'List' and the workflow context strongly imply a non-mutating operation, and the return content is well specified.

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: purpose, return content, and usage flow. Every sentence adds value and there is no redundancy. The information is front-loaded, with the core purpose in the first sentence.

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 zero-parameter listing tool with no output schema, the description provides the essential information: what it lists, what fields are returned, and how to proceed. It fully equips the agent to use the tool in the intended workflow, including the connection to billing_topup.

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 accepts no parameters, so the schema covers 100% of the parameter space. The description adds no parameter information, which is appropriate. The mention of packSku is for the downstream billing_topup call, not for this tool.

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 'List available credit packs for one-off top-ups,' which is a specific verb+resource+scope statement. It clearly distinguishes from billing_topup (which performs the actual top-up) and billing_list_tiers (subscription tiers).

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 to call this tool first, then ask the user to choose a pack, and only afterward call billing_topup with the chosen packSku. This provides clear sequencing and names the alternative tool, leaving no ambiguity about when to use this tool vs alternatives.

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