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

With no annotations, the description carries the full burden. It makes a valuable disclosure: this tool has no financial side effects, preempting a dangerous mis-assumption for a payment-related tool. However, it omits other behavioral traits like error behavior on unknown pack IDs, URL expiry, or authentication requirements.

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?

Two sentences, roughly 14 words, with the core function front-loaded and the critical safety clarification in the second sentence. Every word earns its place; nothing is redundant or filler.

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 low-complexity tool (one simple param, no output schema), the description is reasonably complete: it states the output in prose ('payable HTTP URL and price') and the key exclusion. Gaps remain — what the agent should do with the URL, error behavior, and whether the price is currency-specified — but these are modest for a simple lookup 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 coverage is 0%, so the description must compensate. 'By pack ID' correctly maps the lone `id` parameter to a pack identifier, adding meaning the raw schema lacks. But it adds no further detail about the ID format, where to find it, or validity beyond the schema's maxLength constraint — adequate but minimal compensation.

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 states a specific verb ('Get'), a concrete resource ('a payable HTTP URL and price'), and a lookup key ('by pack ID'). It clearly differentiates this from catalog browsing or sampling tools. The phrase 'payable HTTP URL' is slightly ambiguous about what makes the URL payable, keeping it from a 5.

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?

The explicit negative 'Does not pay, buy, or authorize spending' gives a clear boundary for when NOT to use this tool — it only fetches offer info, payment happens elsewhere. However, no sibling tool is named as the alternative, and the positive usage context is only implied rather than stated.

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