create_billing_checkout

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

Annotations already indicate readOnlyHint=false and non-idempotent, but the description adds significant context: it clarifies that no charge occurs at call time, requires an owner API key, and explains the default value and error behavior. This goes well beyond the structured annotations.

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, each loaded with essential information: the main action, the side-effect caveat, the auth requirement, and the sibling routing. No filler words; key points are 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?

Given the tool has only one parameter, no output schema, and the return value (checkout URL) is explicitly mentioned, all necessary context for correct invocation is present. It also covers auth, default behavior, and error handling, making it complete for an agent.

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 schema provides a description for the 'plan' parameter (with enum and default), but the tool description adds the default explicitly ('plan defaults to developer') and the failure condition ('an unsupported plan fails with invalid_plan'). This enriches the parameter semantics beyond the schema alone.

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 action (create a Stripe Checkout session), the resource (active organization), and the return value (hosted checkout URL). It also explicitly names sibling tools (get_billing_info, create_billing_portal) that serve different purposes, making the tool's 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?

Provides explicit guidance: 'Use get_billing_info to check the current plan and create_billing_portal to manage an existing subscription.' This tells the agent exactly when to use this tool versus alternatives. It also notes the default plan and the error case (invalid_plan) for unsupported plans, which informs decision-making.

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