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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds useful context that results are credential-scoped, but says nothing about pagination, result ordering, or the shape of returned merchant objects, which a listing tool would normally disclose.

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 with zero filler; the scope constraint is front-loaded and the endpoint reference is compact and useful for traceability.

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?

A zero-required-parameter read-only listing tool with fully documented params and annotation-covered safety does not need much more. The only residual gap is that no output schema exists and the description does not hint at what merchant fields come back.

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% — id, slug, and language are all documented in the schema. The description adds no meaning beyond the schema (e.g., whether id and slug combine as AND or OR filters), so the baseline of 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 the merchants") plus the scope constraint ("your key pair can access"), and the underlying endpoint GET /merchants confirms it. The merchant resource is naturally distinct from the sibling tools (bookings, guests, activities, shop items), so no explicit sibling routing is needed.

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 phrase "your key pair can access" implies this is a discovery/listing call scoped to credentials, but the description never says when to call it versus filtering another listing or when-not to call it. Usage is inferable from the name and scope clause rather than stated.

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