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

With no annotations, the description carries the full burden and does real work: it discloses that both keys are returned once and only hashes are persisted (an irreversible, unrecoverable outcome), plus a concrete quota of 25 payments per 30 days and that test mode is uncapped and never reaches a provider. It stops short of stating auth requirements, idempotency on duplicate email, or error behavior, so it is not exhaustive.

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?

Three sentences, front-loaded with the action, then the one-time key warning, then the quota and sandbox semantics. Every sentence conveys information an agent cannot get from the schema or annotations; nothing is redundant.

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 two-parameter onboarding tool with no output schema, the description covers what is returned and the consequences of losing it, plus rate limits and test-mode behavior. Remaining gaps are secondary: idempotency on repeat registration, required auth, and what happens on validation failure.

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 both parameters (name, ownerEmail) are already documented in the schema. The description adds no format or constraint detail for them and instead spends its words on returned keys, which are outputs rather than inputs. 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 ('Register a WavePay merchant account') and none of the ten sibling tools covers account creation, so an agent can route here unambiguously. The first sentence alone settles what the tool does.

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?

Usage is only implied by the nature of the operation (registration is an onboarding step). There is no explicit guidance on prerequisites such as whether an existing account/key is needed first, and no statement of when-not to call it. The free-versus-test tier note hints at mode selection but is not framed as a routing rule.

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