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

Annotations already cover read-only, idempotent, and non-destructive semantics, so the bar is lower. The description adds two behavioral facts annotations cannot express: a per-call price ($0.001 USDC via x402, i.e. payment/auth requirement) and a hard batch ceiling of 20 ids.

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 compact sentences: returned fields first, cost constraint second. No filler, and the most decision-relevant content (scope + price) is front-loaded.

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 an output schema present, return values need not be re-explained, and the cost and batch-size facts round out what an agent needs to invoke it. Missing only error/partial-failure behavior for invalid or nonexistent ids.

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 coverage is 100% so baseline is 3, but the description adds the batch limit ('up to 20') that the schema's 'comma-separated' note does not state, giving concrete guidance on how far the id parameter can be pushed.

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+resource ('Full metadata for ... arXiv ids') and enumerates exactly what metadata is returned. This clearly distinguishes it from siblings like arxiv__search and arxiv__recent, which discover papers rather than resolve known ids.

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 implied by the id-based lookup shape ('for ... arXiv ids'), and the 20-id batch hint suggests bulk use. However, it never explicitly says when to prefer this over arxiv__search or arxiv__recent, nor what happens for unknown ids.

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