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

With no annotations, the description carries the full burden and does disclose meaningful traits: money movement in two phases, card-only restriction, prepaid/virtual refusal, merchant-key auth, and test-mode preview. It omits reversibility, what happens when a scheduled charge fails, and the idempotency/failure semantics of what is clearly a mutating, charging operation.

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 dense sentences with no filler, and the core mechanic is front-loaded before the restriction and auth details. 'mk_test_ previews it' is terse to the point of ambiguity but does not waste space.

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 9-parameter, 7-required mutation with no annotations, no output schema, and 22% schema coverage, the description leaves too much unsaid: the roles of the identity parameters, the meaning of intervalDays, idempotency expectations, and what is returned on success. Adequate only for the headline concept.

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 only 22% across 9 parameters. The description clarifies provider values and the deposit/instalments relationship, but leaves productId, planId, email, externalSubject, intervalDays, and the required idempotencyKey wholly unexplained in both schema and text.

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: take a deposit now and collect the rest on a schedule until paid, which conveys the BNPL plan mechanic in one clause. It is clearly distinct from catalog/pricing/providers siblings, though it never names checkout or subscribe to disambiguate the payment path.

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?

Prerequisites are implied (needs a merchant key; mk_test_ previews), which is useful, but there is no explicit statement of when to choose this over wavepay_checkout or wavepay_subscribe, nor any exclusion beyond card-type refusals. Usage is inferable rather than stated.

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