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

Goes well beyond the readOnly/openWorld annotations by disclosing cost ($0.01 per call), a result ceiling (up to 50 products), and data provenance (Tesco and Asda prices come from the stores' own Google Shopping listings), which warns about potential listing-derived pricing. It does not mention pagination or failure behavior, but the cost and provenance notes are genuinely useful additions.

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 dense sentences with no filler: coverage first, return shape second, commercial and capacity constraints last. Every clause carries information an agent needs before calling.

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 compensates by enumerating the returned fields and the currency, and it adds cost and result-cap details. Only pagination and behavior when a store name is invalid or unlisted remain unaddressed, which is a minor gap for a four-parameter search tool.

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 the baseline is 3, but the description adds meaning the schema lacks: the hard ceiling of 50 products constrains 'limit' beyond its stated default of 20, and 'searches one store' clarifies that 'store' takes a single value per call. The onlySpecials skipping rule is largely restated from 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 concrete verb and resource ('Searches one store by keyword' returning 'products with price in GBP, was-price, unit price, promotion, pack size and link') and names the covered stores. The UK scope plus the store list clearly separates it from the grocery_au_search and grocery_nz_search siblings.

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?

Gives clear context ('Suited to UK grocery price comparison') and an implicit operating constraint that each call searches exactly one store, so multi-store comparison requires multiple calls. It stops short of explicit when-not guidance or naming alternatives for non-UK or non-grocery needs.

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