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

Adds substantive behavior beyond the annotations: the tool may initiate a new comparison (a side effect consistent with readOnlyHint=false), the result includes every offer, exact seller, item condition, and price-check date, and there is a pending/polling lifecycle. It stops short of stating auth requirements or rate limits, but covers the non-obvious traits.

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?

Three sentences, front-loaded with the core action, then return contents, then the pending case. No filler and every sentence carries distinct information.

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?

No output schema exists, so the description carries the return-value burden and does so (ranked products, offers, seller, condition, check date), plus the asynchronous pending flow. An agent has enough to call correctly and interpret the result.

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 documents query, limit, and max_price with examples and defaults. The description adds only indirect meaning ('in their own words', market currency tie-in via the country sites) and no syntax or format detail beyond 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?

States a specific verb+resource ('Compare the prices of a product category or a specific model across merchants') and names the two regional sites. An agent can distinguish this from get_product, get_deals, and get_price_history without opening 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?

Explicitly explains the asynchronous case: if no comparison exists, one is started, status is 'pending', and the agent should re-call with the same query after ~60 seconds. That is real when-to-use guidance, but it never contrasts this tool against its siblings (get_deals, get_price_history, get_product).

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