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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered externally. The description adds that the lookup is store- and postal-code-scoped (price/localization), which is useful context, but discloses nothing about rate limits, failures when a product is unavailable at a store, or result freshness. Adequate but not rich given the lowered bar.

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 dense sentences with the core purpose front-loaded and the input-sourcing guidance trailing. No filler, though the enumeration of six return fields borders on redundant given an output schema exists.

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 a full output schema and read-only annotations, the description covers what an agent needs: purpose, required inputs, and routing to sibling tools. The return-field enumeration is slightly redundant against the output schema, and store-scoping failure modes are unaddressed, but nothing essential is missing.

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% and every parameter is individually documented in the schema (including their source endpoints), so the baseline is 3. The description lists the required params but adds little beyond what the schema already says; the sourcing hint ('from instacart_stores') duplicates the schema's 'from GET /instacart/stores' notes.

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 (Fetch) and resource (one Instacart product's details) with scope qualifier (at a specific store) and enumerates the returned fields (price, sale badge, availability, stock, dietary labels, nutrition). This distinguishes it from instacart_search and instacart_stores without needing their schemas.

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?

Explicitly routes the agent: 'use instacart_stores for store IDs or instacart_search for product discovery.' This covers where to get inputs, but does not state when this tool should NOT be used (e.g. vs nearby/trending variants), so it falls short of full when/when-not guidance.

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