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

Goes well beyond the annotations (which only say not read-only, not destructive, open-world, not idempotent) by disclosing that nothing is charged by the call, that payment happens in the browser, that an existing active plan redirects to the billing page, and that the idempotency_key should be unique and reused on retry. This is exactly the extra behavioral context structured fields cannot convey.

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?

Four front-loaded sentences that each carry distinct information (what it does, no charge, active-plan redirect, agency exclusion, idempotency guidance). Minor slack in phrasing such as 'and give it to the person' but no real waste.

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 2-param mutation with an output schema already covering return values, the description supplies the key scenarios (new purchase, existing-plan change, agency path) and the retry/idempotency contract. Nothing an agent needs to invoke it correctly 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 description coverage is 0%, so the description must compensate. It enumerates the plan values and, more importantly, explains idempotency_key semantics (send a unique key and reuse it on a retry), which the schema only constrains by length. Good compensation, though the plan param is not elaborated beyond the enum already present.

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 (create) and resource (Stripe Checkout link) with clear scope (self-serve Rankwise plan: starter/growth/scale). An agent can distinguish it from siblings like get_plan_and_credits or get_free_ai_audit_link without opening the 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 clear when-to-use context (self-serve plans for this workspace's account) and an explicit exclusion (agency plans are handled by the Rankwise team), plus the alternate path when an active plan exists. It stops short of naming a specific sibling tool as the alternative, so not a 5.

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