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

No annotations are provided, so the description must carry the full behavioral burden. It does not say whether the lookup is read-only, what happens if the domain is unknown, what authentication or rate limits apply, or what data is returned.

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?

It is a single, front-loaded sentence with no filler. The key constraint — one record, looked up by domain — is immediately visible.

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 simple one-parameter getter with no output schema, the description is operationally usable but thin. It omits response shape expectations, not-found behavior, and read-only semantics, which are especially important given there are no annotations.

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 0%, and the schema only types domain as a string. The description adds that domain is the merchant domain used to identify the record, which is meaningful but minimal; it does not specify formatting, normalization, or lookup behavior.

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?

The description states a clear verb and resource (fetch one merchant record) plus the lookup key (domain). It implicitly distinguishes itself from list-oriented siblings like search_merchants by specifying 'one' and 'by domain', but it does not explicitly name an alternative.

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 single-record, domain-keyed nature implies when to use it over search_merchants, but there are no explicit when-to-use or when-not-to-use instructions. An agent can infer the distinction, but the definition does not guide it directly.

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