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

Annotations declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds operational context (returns a Stripe URL, agents cannot pay) and scoping (omit plan for pricing page), but does not mention if the URL is session-bound or its expiry, which would be useful behavioral detail beyond 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?

Two tightly constructed sentences, front-loaded with the primary outcome and immediately followed by critical agent constraints. No 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 no output schema and only two simple parameters, the description is nearly complete: it explains the return type, the human handoff requirement, and when to invoke. It could mention that the URL is ephemeral or session-specific, but the core guidance is sufficient for correct use.

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 50%, with enum values documented in the schema. The description only adds the 'omit plan for the pricing page' behavior, which is helpful but minimal. It does not clarify cycle defaults or accepted values beyond what the enum already provides.

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?

States a specific verb and resource: 'Returns a Stripe checkout URL for a paid plan (or the pricing page)'. It clearly distinguishes itself from siblings like cast_get_account or cast_build_project, and adds a crucial non-agent-actionable boundary by saying the agent cannot pay.

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 a precise trigger: 'Use after a plan-limit or insufficient-credits error.' Also explicitly hands off the payment action to a human, removing any ambiguity about when and how an agent should invoke it.

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