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

Annotations declare non-read-only, non-idempotent, non-destructive, closed-world, which matches a paid run-and-return operation. The description goes beyond them with the credit cost, the automatic refund on failure, and the OPN account requirement — the key behavioural facts an agent needs before invoking a metered tool.

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 sentences, front-loaded with the core action and scale, then the operational constraints. Dense but essentially every clause carries information; no padding or repetition.

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?

No output schema exists, so the description must carry return semantics — and it does, naming grade, reasoning, EPR eco-modulation impact and options to reach a higher grade. Combined with cost and auth disclosure, an agent has everything needed to call this correctly.

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?

Only one parameter and schema description coverage is 100%, so the schema already documents the 'input' string fully. The description's enumeration of substrate, layers, inks, closures and adhesives largely restates what the schema describes, adding little beyond it.

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 ('Grade a packaging structure') plus the exact framework and output scale (EU PPWR recyclability, A to F) and the inputs considered. An agent can distinguish this from siblings like packiq_epr_fees or packiq_quote_analysis without opening any schema.

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?

Gives clear preconditions: requires the user's OPN account and costs 4 PACKIQ credits, refunded automatically on failure. It doesn't explicitly say when to prefer this over neighbouring tools such as packiq_epr_fees, but the cost/auth context is unusually concrete.

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