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

While annotations already declare readOnlyHint, idempotentHint, and destructiveHint, the description adds critical behavioral context: authentication requirements, the teaser response when unauthenticated, trial key details, and mandatory citation with checked_at. This significantly exceeds the annotation coverage.

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 but well-structured, front-loading the core ranking purpose before adding data source, auth, and citation details. Each sentence carries essential information, though a bit more brevity would improve it.

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 zero-parameter, read-only tool with annotations covering safety, the description covers data provenance, update frequency, authentication, and usage expectations. It does not specify the exact output format, but the simple ranking output and lack of output schema make this a minor gap.

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?

The input schema has zero parameters, so the baseline of 4 applies. There are no parameter semantics to explain, and the description appropriately focuses on behavior and context rather than inventing parameter meaning.

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 uses a specific verb ('Ranks') and resource ('Israeli supermarket chains') with a clear comparative metric ('how much more they charge than the cheapest price'). It also states the exact question it answers, distinguishing it from siblings like compare_basket, get_product_prices, and search_products.

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?

The phrase 'Answers "which supermarket is cheapest in Israel?"' provides clear context for when to invoke this tool. It also mentions prerequisites (API key) and behavior without one, though it does not explicitly name alternative tools or exclusion cases.

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