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

The description discloses key behavioral traits beyond the annotations: it is a fallback, opens external Checkout, and that PromptFax treats webhook-confirmed authorization as payment truth, not the browser redirect. Annotations only indicate non-destructive and open-world, so the description adds valuable safety context.

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 very concise at two sentences, with the main purpose front-loaded. Every sentence adds essential information without redundancy 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?

Given the tool's moderate complexity and the presence of an output schema, the description is complete. It covers the tool's role, when to use, behavioral nuances, and workflow context (widget vs. non-widget), leaving no major 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?

Schema coverage is 100% with detailed descriptions for each parameter. The description does not add significant new meaning beyond what the schema already provides. It restates the parameter usage (e.g., sessionId for session-backed workflow) but does not expand on constraints or formats.

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 clearly states it is a fallback/non-widget tool for starting external Stripe Checkout after the user accepts a pay-per-use quote. It distinguishes itself from siblings by explicitly noting it should not be called after start_session in widget sessions, making its unique role clear.

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 explicit guidance on when to use (after user accepts a pay-per-use quote) and when not to use (in widget sessions after start_session). It also explains the payment authorization logic (webhook vs. redirect), giving clear context for correct invocation.

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