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

Annotations already declare readOnlyHint=false, openWorldHint=true, and destructiveHint=false, and the description is consistent with that, adding that an external Stripe checkout is created and a one-click URL is returned. It also discloses the auto-detection rules (Free → Creator, Creator → Team). It doesn't say whether repeated calls create multiple checkout sessions or what permissions/billing access the user needs, which keeps it from a 5.

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?

Three sentences, front-loaded with the action, then the default behavior, then the invocation trigger. Every sentence carries distinct information with no repetition.

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 output schema, the description appropriately states the return value (a one-click checkout URL). Two optional enum parameters are fully documented, and the trigger condition plus auto-detection cover everything an agent needs to invoke 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% and both parameters have enums with full descriptions, so the schema already carries the semantics. The description's mention of the `plan` override merely restates the schema's auto-detection note and adds nothing about `interval` beyond what the schema says.

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 ('Creates a Stripe checkout link') plus the exact goal (upgrade the ShortSync plan). No sibling tool touches billing or upgrades, so an agent can identify this immediately from the name and description pair.

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?

Explicitly names the trigger: 'Call this when a publishing or scheduling tool returns an upload-limit or subscription error.' It also explains the auto-detect default and the `plan` override path, so both the entry condition and the escape hatch are clear.

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