Cheapest Price

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful behavior: the price is checked live, localized to the shopper's country and currency, and aggregates specific retailers rather than a single source. It stops short of mentioning latency, caching, or failure modes.

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?

Two sentences, front-loaded with the core purpose and followed by retailer detail. Slightly redundant — 'lowest current price for a product' appears in both sentences — but there is no filler and nothing off-topic.

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 carries the return-value burden and does so: lowest price plus comparison links from named retailers. Combined with 100% parameter documentation and full annotations, an agent has enough to call it correctly; only edge details (partial results, currency rounding, rate limits) are absent.

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 q, used and country are all documented in the schema; baseline is 3. The description's 'checked live in the shopper's own country and currency' echoes the country parameter's default behavior but adds no syntax or constraints beyond what the schema already states.

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 resource (lowest current price for a product) and enumerates the sources checked (eBay, Best Buy US, Amazon, local shops) plus the compare-links output. It is clear and concrete, though the opening sentence largely restates the title rather than adding a distinct verb or scope statement. No siblings exist, so there is nothing to differentiate against.

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?

Usage is implied — check this when you want a live cross-retailer price — but the description states no explicit when-to-use or when-not-to-use conditions and names no alternatives. With no sibling tools, the routing burden is low, so 3 (minimum viable) is appropriate.

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