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

Beyond the readOnly/openWorld/idempotent annotations, the description discloses materially useful context: what each returned item contains (role, price, rating, order count, link, alternatives), that prices are localized to the delivery country's currency and include delivery, that free shipping is the default so the total equals what the buyer pays, and that links are affiliate links with no buyer price impact. That is a lot of behavioral value the structured fields do not carry.

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 sentences, front-loaded with what the tool produces before drilling into item fields and pricing/affiliate caveats. Dense but nearly every clause carries decision-relevant information; the parenthetical commission note could be trimmed slightly.

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?

With no output schema, the description takes on the burden of describing the return shape, which it does well (per-item fields, alternatives, localized pricing). All seven parameters are documented in the schema, so the only real gap is the missing guidance on how this relates to search_products for single-item lookups.

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 still adds meaning by explaining that budget is a hard total ceiling, that pricing is in the delivery country's currency, and that free_shipping_only is a default filter on listings rather than a cosmetic flag. Only 'priority' and 'recipient' semantics are left entirely to the schema.

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 names a specific verb (plan/fill) and resource (a basket of complementary products) with concrete example needs ("home gym starter set", "camping cooking gear") and budget scoping. An agent knows exactly what it gets, but the definition never contrasts itself with the sibling search_products, so the distinction (one-need multi-item basket vs. per-query product search) is left to inference.

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?

Clear context for use: a single need plus a budget, resulting in a complementary set rather than a single product. Exclusions and the alternative (search_products) are not stated, keeping it below a 5.

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