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

Annotations already declare readOnlyHint and openWorldHint, and the description aligns with these while adding meaningful behavioral context: result ordering is by likelihood of working, results are not guaranteed, and empty lists have a defined meaning. This goes beyond the structured annotations and helps the agent set user expectations.

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 concise and front-loaded: it states the purpose and input format first, then explains result ordering and caveats. Every sentence contributes useful information, with no filler or redundant phrasing.

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 low-complexity read-only tool with a high-coverage schema and an output schema, the description covers all essential context: what to pass, what the tool returns, how to use the results, and important limitations. Nothing critical is missing for an agent to invoke it correctly.

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 input schema already documents both parameters. The description repeats the store parameter semantics but does not add new parameter-level detail beyond the schema. The baseline of 3 is appropriate because the schema carries the parameter documentation burden.

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 clearly states the tool's function with a specific verb and resource: find coupon/promo/discount codes for an online store. It also specifies the accepted input format (store domain or any store URL), making it unambiguous. No sibling tools exist, so differentiation is not required.

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 description gives explicit usage guidance: pass a store domain or any store URL, and explains how to interpret and act on results (try codes from the top, keep the one that lowers total the most). It also manages expectations by noting codes may expire or carry restrictions, and that an empty list means no known codes.

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