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 the credit cost per store ('one SerpAPI credit PER STORE (6 by default)'), the 5-minute server cache, that shipping is never folded into price_pln, that foreign prices are Amazon's own PLN conversion with Polish VAT, and that a failing store surfaces in `marketplaces` rather than as an error.

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?

Cost and defaults are front-loaded, which is right. But a large block is spent restating the full result shape and every product field — an output schema exists, so this is mostly redundant bulk that pushes the genuinely useful notes (asin_matches, error handling) toward the end.

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 17-parameter, 10-marketplace fan-out with no annotations, the description covers cost, caching, currency semantics, failure modes and ASIN grouping — everything an agent needs to call it correctly. Return values are covered by the output schema, and the extra shape dump, while verbose, leaves no ambiguity.

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 goes beyond it by explaining what shipping_location actually changes (delivery cost in `delivery`, no delivery guarantee under 'local', NBP conversion) and that min_price_pln is sent in local currency with 10% slack then enforced exactly. It doesn't similarly enrich sort vs order_by, which remain schema-only.

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 with scope: 'Run one query on several Amazon stores in parallel ... and merge the results in PLN'. The multi-store merge is precisely what separates it from amazon_search, and the default sort ('cheapest first') is named up front.

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 concrete usage advice — 'Use a precise query (brand + model) and min_price_pln to keep accessories out of a price-sorted list' — and explains the shipping_location 'PL' vs 'local' tradeoff as a decision. It never names amazon_search or amazon_product as the alternative for single-store or single-product lookups, so the when-not is left implicit.

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