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

Adds real context beyond the annotations: the tool produces a URL for a human rather than mutating plan state, webhooks own the DB write, and operator tokens must pass team_id while team-scoped tokens cannot target another workspace. It does not address repeat invocation (idempotentHint=false implies a new Checkout session each call) or link expiry, which are the remaining behavioral gaps.

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?

Front-loads the trigger well, but roughly a third of the text is duplicated: the plan limits are stated once as trigger conditions and again as a 'Free:' / 'Yearly:' spec sheet, and 'Use create_upgrade_link to hand a human a Stripe Checkout (or Customer Portal) URL' restates the opening. Pricing tier detail crowds out the actionable call instructions.

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 two-optional-parameter tool with no output schema, everything needed is present: when to call, what URL comes back, token scoping, the webhook ownership of plan state, and the error surface ('other values return plan_limit'). No essential invocation detail is missing.

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%, so baseline is 3; the description earns above that by explaining the semantics the enum alone cannot convey — omitting product on a yearly team yields a Customer Portal URL, while product=expansion adds a $99/year 5,000-submission pack. The team_id guidance (operator token vs team-scoped token) also reinforces the schema note.

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+resource (create an upgrade/billing link) and immediately names the artifact it returns: a Stripe Checkout URL (or Customer Portal URL). No sibling tool touches billing, and the description makes the billing/plan boundaries unmistakable.

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?

Gives explicit triggering conditions ('when a free team is blocked on the 3-project, 100-submission, or one-workspace limit'), an explicit branch (already yearly → omit product for a Portal URL), and an explicit prohibition ('Do not change plan in the database — Stripe webhooks do that').

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