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

Annotations already declare readOnlyHint/idempotentHint=true and destructiveHint=false, so the safety profile is covered, and the description adds genuinely new context: nothing is charged until the order is placed, and the concierge handoff creates no durable quote, reserves no stock, and purchases nothing. It does not cover auth needs or failure behavior when the re-check fails.

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 trigger and effect, and every sentence carries information (trigger, required inputs, return semantics, handoff caveat, sequencing). The middle sentence is dense and run-on, but there is no filler.

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-required-param tool with two distinct outcomes, the description covers both branches, the sequencing with get_buying_options, and the non-charging guarantee; an output schema exists so return-format detail is not needed. Only the failure path when the offer re-check fails is unaddressed.

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, but the description adds meaning beyond the schema by tying parameters to the source call ('retain its exact quantity, ZIP and fulfillment_mode' from get_buying_options) and clarifying the variant product_id requirement. This cross-parameter guidance goes past the field-level schema text.

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?

The description states a specific trigger ('Call when the shopper has chosen to buy') and the concrete effect: re-checks the offer at that quantity and returns a checkout_url with the item added to the shopper's basket. It also distinguishes the two output paths (JENNi checkout vs. a concierge product-page handoff), so an agent can tell it apart from siblings like get_buying_options and get_product.

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?

It gives an explicit trigger condition and preconditions: store_id must be an offer with is_eligible_checkout true or a concierge offer, and the inputs should be retained from get_buying_options. It stops short of naming an explicit 'do not use when' case, but the when-to-use context is unambiguous.

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