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

readOnlyHint=true already tells the agent this is a safe read, and the description adds the backing endpoint (GET /shop/items), which is minor but real context. It says nothing about pagination, result caps, or whether inactive items are returned by default—behavioral facts an agent would want before calling.

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 short sentences, front-loaded with the purpose and the clarifying gloss before the ancillary endpoint reference. Nothing is padded, though the trailing API endpoint line is of marginal value to an agent.

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-required-param, read-only list tool with full schema coverage and annotations covering the safety profile, the description is sufficient to select and call it. The only real gap is that no output schema exists and the description doesn't hint at the shape of the returned list.

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 schema already explains all five parameters including their array semantics. The description restates the merchant/category/active filters but adds no meaning beyond them and omits the id and language params entirely. Baseline 3 applies.

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 ('List shop items') and clarifies the domain term with a gloss ('extras sold with activities'), which an agent couldn't infer from the name. It also names the filter dimensions. It does not explicitly distinguish itself from the list_activities/list_merchants siblings, so it stops short of a 5.

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?

'Filterable by merchant, category and active state' implies the retrieval use case but never states when to reach for this tool versus a sibling list_* or a get_* lookup. There are no exclusions or prerequisites, leaving usage to inference.

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