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

Annotations already declare readOnlyHint and openWorldHint, so the read-only nature and open-web source are covered. The description adds genuinely useful context beyond them: $0.01 per call cost, a 50-product ceiling, and the exact fields returned. It does not cover pagination, empty-result behavior, or freshness/latency of "live" prices.

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 source and action, then return fields, then usage and cost. The return-field enumeration earns its place because no output schema exists; only the repeated "New Zealand" mention is mild redundancy.

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 usefully enumerates return fields, and it discloses the per-call price and result cap an agent needs to budget calls. Remaining gaps are minor: no statement about zero-result behavior or whether store is effectively fixed to woolworths-nz.

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 all four parameters are already documented, and the description adds only the "up to 50 products" cap that constrains limit. The store parameter's allowed value and the string-typed boolean semantics of onlySpecials are left to 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 and resource: "Searches by keyword and returns products with price in NZD" from Woolworths New Zealand. The geographic scoping (NZ, formerly Countdown) is enough to separate it from grocery_au_search and grocery_uk_search, though it never names those siblings explicitly.

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?

"Suited to New Zealand grocery price and specials questions" gives clear usage context, and the field list hints at specials/Club-price lookups. There is no explicit when-not-to-use guidance (e.g. use the AU/UK tools for those regions), so it stops short of full routing guidance.

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