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

Beyond the annotations, the description discloses the external Stripe handoff (consistent with openWorldHint), that saving a card performs no charge, and that the first charge only occurs after team approval. It does not cover failure modes or what happens if the person abandons the Stripe page, which is a minor gap given the annotations already flag non-read-only, non-idempotent behavior.

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?

Four short sentences, front-loaded with what the tool does, then sequencing, then the critical no-charge reassurance. Every sentence carries information an agent needs, and nothing is repeated from the title or annotations.

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?

With no parameters and no output schema, the description supplies the prerequisites, the external redirect, and the charge semantics needed to call it correctly. It stops short of describing what the call returns (for example a URL or a status flag), which is the one thing an agent would still have to discover empirically.

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 takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a parameterless tool applies. The description correctly frames the person/campaign context as implicit state rather than arguments.

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 and resource: it checks for an existing card on file and, when absent, provides a secure Stripe page to save one. That is clearly distinct from siblings such as submit_campaign, pause_ads, or request_change, so an agent can identify the tool without inspecting its schema.

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 gives explicit sequencing ('step 2 after submit_campaign when no card is on file') and a concrete re-invocation rule: call it again once the person says they have saved the card, to confirm. Both the when-to-use condition and the follow-up pattern are named, leaving nothing to inference.

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