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

readOnlyHint=true already tells the agent this is a safe read, so the description's burden is reduced. The helpful addition is the "Admin API: GET /v1/admin/merchant" note, which hints at the underlying access level. It discloses nothing further about response shape or errors, which is acceptable given the annotations cover the safety profile.

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 tight sentences: the payload fields come first, then the usage cue and endpoint reference. No filler, nothing an agent would have to skim past.

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 no-argument read of a single object with no output schema, the description lists what comes back and how to invoke it. An agent has everything needed to call it correctly without further context.

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 and the schema is empty, so there is nothing parameter-related for the description to explain. The description correctly signals the caller needs no arguments, matching the baseline for zero-param tools.

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?

Specific verb+resource ("Get the merchant account") followed by an enumeration of the fields returned (name, country, currency, timezone, languages, plan, enabled features). This clearly separates it from siblings like twicecommerce_get_customer or twicecommerce_get_order, which target different resources.

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?

"Good first call" gives the agent a concrete routing cue for when to reach for this tool, and the account-level scope implicitly excludes per-record lookups. It stops short of explicitly naming an alternative or a when-not condition, so it falls just under the top mark.

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