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

Annotations already declare idempotentHint=true, destructiveHint=false, and readOnlyHint=false. The description adds the server-side key requirement and the return type ('Returns url'), which is useful, but it doesn't disclose side effects like creating a Stripe session or failure behavior. Given the annotations carry the safety profile, this is adequate but not rich.

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 with zero fluff. The core action and key prerequisite are front-loaded. Every word adds value.

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 simple tool with no output schema, it tells the agent what it returns (url) and the required environment variable. It doesn't mention error scenarios or what happens if the key is missing, but for this level of complexity it is sufficiently complete for an agent to call it correctly.

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 description coverage is 100%, so all three parameters are documented in the schema. The description only re-states the enum values (Starter/Pro) and adds no additional meaning for email or client_id. Baseline 3 is appropriate since the schema does the heavy lifting.

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 ('Create'), a concrete resource ('Stripe Checkout URL'), and the plan scope ('Starter or Pro'). It is immediately clear what this tool does and how it differs from billing-status or messaging tools in the sibling set. No ambiguity.

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 a clear usage context ('so you can hand the human a pay link') and a prerequisite ('Requires STRIPE_SECRET_KEY'). It doesn't explicitly mention when not to use it or name alternatives, but the context implies it's for upgrade payments. This is better than no guidance.

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