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

readOnlyHint=true already declares the safety profile, and the description adds value beyond that: it discloses that the result is scoped to the calling token (no merchant id argument), what fields come back, and that the call is cheap/near-free. It stops short of describing rate limits or error behavior for an invalid token.

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 core purpose and payoff, followed by the endpoint reference. Every clause carries information and nothing is padded.

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 usefully summarizes the shape of the return (business name, email, country, currency), and for a zero-parameter read-only call there are no other gaps an agent would need filled before invoking it.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a no-arg tool is a 4. The description correctly conveys that identity comes implicitly from the token rather than an argument.

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 (the merchant account this token belongs to), and enumerates the returned fields (business name, email, country, currency). This is clearly distinct from the get_/list_ siblings, which all target other resources such as customer, item, or receipt.

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 frames when to reach for it: 'A cheap way to confirm the token works,' which tells the agent this is a lightweight credential sanity-check. It does not name an alternative tool or state exclusions, but for a token-scoped singleton fetch none are really needed.

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