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

Annotations only declare readOnlyHint=false and destructiveHint=false; the description goes further by bounding the side effect ('does not send money or debit a wallet') and naming the prerequisites for actual payment (spending authority, compatible signing wallet). It stops short of describing return values, expiry, or rate limits, but adds genuinely useful context beyond the structured fields.

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 with the core action front-loaded and no filler. The final sentence stacks two ideas (payment prerequisites and guest registration) but remains readable.

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 and only minimal annotations, the description carries meaningful burden, and it does cover the key behavioral fact that no funds move. It is still missing parameter guidance and any indication of what a quote returns, which matters for an agent that must decide how to proceed after calling 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?

Schema description coverage is only 33%—account_ref is documented but method_id and package_id rely on enums alone. The description mentions 'prepaid package' and payment method concepts only obliquely and never names method_id, package_id, or account_ref, so it does not compensate for the coverage gap.

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?

The description names a specific verb ('Quote') and resource ('prepaid package or current custom option'), which is more precise than the tool name 'create_invoice' implies. However, it never distinguishes itself from closely related siblings such as eclypse_guest_checkout or eclypse_preview, leaving the agent to infer the boundary between quoting and checking out.

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?

It provides situational context—payment requires existing spending authority plus a compatible signing wallet, and guest purchases need no registration—which implies when the tool is usable. But it never states when to pick this tool over alternatives like eclypse_guest_checkout, so the routing decision is left implicit.

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