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

Annotations already indicate read-only and idempotent behavior, and the description adds valuable context: listing is always free, offers are labeled 'Sponsored', and early-bird mode returns purchasable=false. This goes beyond the structured metadata and helps the agent understand expected response semantics.

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 long, front-loaded with the main purpose, and every sentence adds meaningful information: what is listed, what is returned, and the early-access behavior. No filler or redundancy.

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 the absence of parameters, the presence of an output schema, and strong annotations, the description fully covers the situational nuance (early access, purchasable flag, Sponsored labeling). Nothing important is missing for an agent to invoke and interpret this tool 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 tool has zero parameters, so the input schema carries no burden. The description appropriately focuses on the returned data (name, effect, price, purchasable flag) rather than input semantics, which is sufficient for a parameterless list operation.

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 uses a specific verb ('List') and a clear resource ('optional paid add-ons (offers)'), with details about name, effect, and price. It distinguishes itself from siblings like create_checkout by explicitly framing list_offers as the lookup step before checkout.

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 description explicitly says 'Call this to see what's purchasable before create_checkout,' giving a clear when-to-use directive. It also explains the early-access caveat, telling the agent that offers may not be purchasable yet and will show purchasable=false, which prevents misuse.

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