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

Beyond the readOnlyHint annotation, the description discloses that the tool may advance an internal verified payment state, a non-obvious side effect that an agent would otherwise miss. It also clarifies that it is read-only from the agent perspective, reconciling the annotation with the internal state change. This adds significant behavioral nuance.

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, each earning its place: the first states the primary action and condition, the second clarifies read-only semantics and the internal side effect. No fluff; the key information is front-loaded.

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 tool with no output schema, the description does not explicitly describe the returned 'promotion order state' or the verification result. It gives enough context to guess, but an agent would be unsure of the exact output shape, edge cases (e.g., no checkout session), or error behavior. The description is adequate but leaves gaps.

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?

With 0% schema description coverage, the description carries the burden for explaining order_id. It only implies the parameter through 'promotion order state' and 'checkout session', but never explicitly states what order_id refers to, its source, or format. The inference is possible but the description fails to compensate for the schema gap.

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 specific verbs ('Read', 'verify') on a clear resource ('promotion order state', 'payment'), and distinguishes this from sibling tools like prepare_event_promotion_checkout and search_events by focusing on status/verification. The title adds 'payment and placement status', and the description further specifies the independent verification behavior, making the tool's 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 provides a clear usage context: read order state and verify payment, especially when a checkout session exists. However, it does not explicitly contrast with sibling tools or state when not to use it, so it lacks explicit exclusions/alternatives.

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