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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered; the description adds genuinely useful behavior beyond that: de-duping against already-tracked ASINs, ranking order, returned fields (brand, title, price, fulfillment, amz/fba pct), and all-filters-default-to-no-filter. Minor ding: the description scopes to 'Amazon US/UK' while the schema's marketplace_id supports 12 marketplaces, an internal inconsistency the agent may trip on.

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?

The description is dense and front-loaded: core behavior first, then de-dup behavior, then trigger phrases, then payload, then filters. The filter enumeration is long but organized with semicolons and family groupings, so every sentence earns its place. It is slightly over-stuffed but not bloated.

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 21-parameter tool with no output schema, the description covers the essential gaps: how to invoke (ASIN or operator_name), what each candidate carries, ranking and de-dup behavior, marketplace scope, and the filter list. It falls short of a 5 because of the US/UK vs multi-marketplace inconsistency and silence on the limit parameter's default/existence.

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?

With only 33% schema description coverage, the description partially compensates by grouping filters into families (sourcing_score, est_units_30d, buybox_avg_price, resold_by_contains, and the 'shared product/fulfillment block') and stating the no-filter default. But it does not clarify individual meanings for the 14 undocumented parameters (e.g., min/max_fulfillment_amz_dom_pct, product_brand_contains), and the 'shared block' concept is only hinted at, not explained.

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 verb and resource: given an ASIN or operator name, find the OTHER ASINs those operators also resell, ranked by sourcing fit then estimated 30-day sales. It adds distinguishing scope (arbitrage sourcing feed, de-duped to surface NEW candidates) that separates it from siblings like operator_top_asins or find_sourcing_opportunities. The core behavior is unambiguous.

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?

Explicit trigger phrases are given ('what else does this seller carry', 'find more like this from the same operators', 'arbitrage leads from this ASIN's sellers'), which clearly establishes when to invoke this tool. However, no alternative tools are named and no when-not-to-use conditions are stated, so it stops short of full routing guidance.

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