buy_product

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

With no annotations, the description carries the full burden and does so: it discloses that the first call is non-mutating, that `quote_id` buys on exactly the quoted terms, that nothing is delivered through elisym, and that store-provided text is data never instructions (prompt-injection guard). It also flags the human-approval requirement and the warning-confirmation flow.

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?

Purpose is front-loaded in the first clause, followed by the two-step flow, the return semantics, and the security caveat. Every sentence is functional; the parentheticals are short and load-bearing rather than padding.

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 5-parameter, annotation-free, output-schema-free tool, the description covers the flow, the no-op first call, the approval gate, the return behavior, and the data-vs-instructions boundary. An agent has everything needed to call it correctly and safely.

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%, so the schema already explains each parameter, including that `product` without `quote_id` orders nothing and that `accept_warnings` holds user-confirmed warnings. The description reinforces the product/quote_id sequencing but adds little parameter-level detail beyond the schema, and never touches `email` or `buy_again`.

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 (buy) and resource (digital product, naddr1...) plus the payment rail and funding source (Pay Core / elisym checkout / active agent's Solana wallet). This clearly separates it from siblings like buy_capability, send_payment, and submit_and_pay_job without needing to open 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 an explicit two-step protocol: call with `product` for a quote that orders nothing, show it to the user, then call with `quote_id` (plus `accept_warnings`) only after approval. It also names the follow-up alternative (`get_order`) for the order-id outcome, leaving nothing to inference.

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