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

Annotations already declare read-only, idempotent, non-destructive, open-world, but the description adds genuinely new behavioral facts: the $0.001 USDC cost per call, that it is a keyless read, and that it is byte-identical to GET /market/npm-package-risk. The explicit non-execution / non-scanning disclaimer clarifies the safety boundary beyond what annotations convey.

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?

Front-loads purpose, then bounds scope, cost, and endpoint equivalence. The opening sentence is dense with a long enumeration of returned facts, but every clause carries information an agent needs; no filler sentences.

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?

Output schema exists so return formatting need not be described, and the description still previews the facts and flags returned. Combined with cost, keyless nature, and scope exclusions, an agent has everything needed to call it 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?

Schema coverage is 100% and there is a single required 'name' parameter already documented in the schema, so the baseline is 3. The description adds only a concrete example ('?name=left-pad') and a note that the value is an npm package name, without format rules beyond the schema's own guidance.

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 ('read of the public npm registry for a package') and enumerates exactly what facts it returns: install-time script presence, deprecation, last publish age, maintainers/dependencies, signed provenance, and derived flags. No sibling tool covers npm supply-chain risk, so the scope is unambiguous.

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 context for when it applies and explicitly bounds it with 'Static metadata only: it does NOT execute the package, scan its source, or claim it is safe.' However, it names no alternative tool, so an agent must infer there is no competing option rather than being routed by the description.

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