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

Goes well beyond the annotations by clarifying that the call creates a live payment session but charges nobody by itself, that the return value is a URL, and that payment must be completed out-of-band by the human. That is a material behavioral fact (side effects, money movement boundary) not derivable from readOnlyHint=false / openWorldHint=true alone.

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 purpose and the outcome, then the safety instruction, then the precondition — a sensible order. The parenthetical price/refund detail is useful but the sentence is slightly overloaded; minor trimming would tighten it.

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-parameter tool with an output schema and full annotation coverage, the description supplies everything an agent needs: what it creates, what it returns, the payment boundary, and the freshness precondition on the required argument.

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 the baseline is 3; the description adds a real constraint the schema cannot express — the submission_id must originate from submit_pwa and be less than 30 days old. The optional email parameter is left entirely to the schema, which is acceptable given its full documentation.

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 (create a Stripe Checkout link) plus the object it acts on: upgrading an existing submission to Fast-Track. It also names the concrete outcome ($19.99, 48 h publication, refund policy), which no sibling tool offers, so the agent can distinguish it from get_pwa/submit_pwa immediately.

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 prescribes the workflow: give the returned URL to the person you are working for and never attempt to complete the payment. It also states a hard precondition (submission_id from submit_pwa, under 30 days old), which is exactly the when-to-use/when-not guidance an agent needs.

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