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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds genuinely non-derivable context: pay-per-call pricing ($0.001 USDC via x402 on Solana), an equivalent HTTPS endpoint, and an explicit boundary case (sheets bigger than C0 have no C envelope). It stops short of noting whether a failed/unsupported sheet still incurs a charge.

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?

Purpose is front-loaded and the three example sentences are dense with useful information. The pricing and HTTPS-endpoint details are appended somewhat abruptly after the domain content, but nothing is wasted.

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, the description does implicitly convey the return content (smallest C envelope, DL flat-vs-thirds verdict) and it covers access mechanics. However, the missing definition of the single input, plus no statement of what happens for unsupported inputs, leaves the definition incomplete for correct invocation.

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 0%, so the description carries the full burden for the required `name` parameter, yet it never states that `name` is a paper-size designation. The agent must infer the input format from incidental examples ("C4 holds A4", "A4 folded in thirds") and gets no guidance on accepted labels or the 8-character limit.

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 computation: the smallest ISO C envelope that holds a given sheet flat, plus whether DL holds it flat or folded in thirds. Concrete examples (C4 holds A4) make the domain unambiguous. It does not differentiate itself from likely siblings such as paper_size, paper_fit, or paper_scale, which is the only thing keeping it from a 5.

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 purpose statement; there is no explicit when-to-use or when-not-to-use guidance. Given several near-neighbour siblings (paper_fit, paper_size, paper_scale, paper_next, text_fit), a sentence routing the agent among them would have earned a higher score.

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