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

Annotations declare a non-read-only, non-destructive, non-idempotent, closed-world mutation, and the description adds real context beyond that: the amount is derived from FastCAC pricing minus any discount, the caller never sees card details or the payment link, and the outcome arrives as a system event rather than a return value. That last point is especially valuable since there is no output schema. It stops short of saying what happens on a duplicate call, which matters given idempotentHint=false.

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 short sentences, front-loaded with the action, then amount semantics, then outcome semantics. Every sentence carries distinct information and nothing is repeated from the schema or annotations.

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 one-parameter tool with no output schema, the description covers the key surprises: price derivation, opacity of the payment link, and asynchronous result delivery. The only meaningful gap is the meaning of business_id and the behavior when the form is incomplete or the call is repeated.

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 single parameter business_id has 0% schema description coverage and the description never mentions it at all — no indication of whether it identifies the business being registered or the registration itself. With low coverage the description is expected to compensate, and here it does not.

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 action and resource: 'Show a Pay button for a registration,' which is clearly distinct from siblings like calculate_cac_fees or apply_discount_code. The purpose is immediately understandable, though it never names the sibling tools it sits between in the payment flow.

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 phrase 'once its form is complete' gives one precondition for use, which is genuine usage guidance. However, it does not mention the related siblings (apply_discount_code, calculate_cac_fees) or what to do if the form is not complete, leaving the agent to infer the surrounding workflow.

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