Check an npm package before installing it

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

Annotations already cover readOnly/idempotent/non-destructive. The description adds genuinely new behavioral facts: it never downloads or runs the package code, and it enumerates the signal categories it evaluates. It stops short of describing result shape, latency or rate limits, so it's strong but not exhaustive.

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-loaded with the use case, then a dense but well-organised enumeration of checks, then two short sentences for the safety guarantee and accepted input formats. 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?

No output schema exists, so the description must convey what comes back; it names the finding categories, which is close to sufficient. It doesn't say how findings are surfaced or formatted, a minor gap for a read-only inspection tool with complete annotations.

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% with a single string param, but the description goes beyond the schema's bare examples by defining accepted forms: bare name, scoped @scope/name, name@version, and a pasted install command — the last of which the schema never mentions.

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 (look up / check) and resource (npm package) and enumerates exactly what dimensions it covers: removal by npm, OSV.dev malicious/vulnerable reports, install script behavior, look-alike names, hijack signals. It is unmistakably distinct from the scan_message/scan_address/compare_addresses siblings.

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?

"Look up an npm package before `npm install`" gives a clear trigger context and temporal placement. It doesn't name alternatives or state when not to use it, but the sibling tools operate on entirely different domains so no routing conflict exists.

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