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

Beyond the annotations (readOnlyHint=false, idempotentHint=false), the description discloses the key behaviors an agent would otherwise get wrong: the call itself moves no money, a URL is returned for the user to complete payment, and passing an email tied to an existing company attaches the subscription to that company. That last detail is a real side-effect disclosure no annotation covers.

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-loaded with the verb, resource and return value in the first two lines, and each following sentence carries information (no-charge, existing-company attachment). Slightly instruction-flavored ('Show them the plan...'), which is useful but reads more like prompt text than tool documentation.

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?

An output schema exists, so the description needn't explain the response shape, and it covers the critical non-obvious semantics (no immediate charge, existing-company linkage). Remaining gaps are the undocumented optional parameters (coupon_id, company_name, redirect_url_cancel) and failure/expiry behavior for the generated link.

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%, and the description only reinforces what the schema already says for email ('company is found or created from it') and stripe_price_id ('from list_plans'). coupon_id, company_name and redirect_url_cancel get no added meaning anywhere, so the description does not compensate for the coverage gap.

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?

Specific verb + resource: 'Create a Stripe Checkout link for a plan', plus the concrete return ('Returns a URL'). It is distinguishable from siblings like open_billing_portal, provision_customer and list_plans — this is the link-generation step, and the description makes that role obvious without opening a schema.

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 real usage context: it does not charge anyone, the user must open the link and pay, and the agent should present the plan, price and change set first. It does not name the adjacent alternatives (open_billing_portal, provision_customer) or state exclusions, so it falls short of a 5.

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