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

Annotations already communicate that this is non-read-only, destructive, and idempotent. The description adds useful context by tying the call to sponsored results and funnel stages, but it does not explain billing consequences or the need for a valid token. Given the annotations, this is acceptable but not rich.

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 short sentences with no filler. The action is front-loaded, and the funnel stages are enumerated compactly. Every sentence contributes to correct invocation.

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 3-parameter tool with full schema coverage, output schema, and annotations, the description plus schema provides enough context to call the tool correctly. A small gap is that it does not explicitly warn about the monetary/destructive nature or require a token, but these are covered by annotations and schema.

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%, and the schema already documents token, event_type, and order_value with clear descriptions. The description does not add parameter-level detail, but with full schema coverage the baseline of 3 is appropriate.

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 names a specific verb ('fire'), a resource ('billing event'), and the triggering context ('when acting on a sponsored result'). The funnel-stage enumeration also distinguishes it from sibling tools like sponsored_search or brand_spotlight, making its purpose unmistakable.

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 to call the tool at each funnel stage and lists the stages: context, shortlist, recommendation, purchase. It does not explicitly name alternatives or say when not to call it, but the sponsored-result condition provides clear usage direction.

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