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

Beyond the read-only, idempotent, non-destructive annotations, the description discloses important behavior: found:false means no published verdict rather than a clean result, nothing is downloaded or scanned, and the request names the package to the server. That last point gives useful privacy/behavior context not covered by annotations.

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?

The purpose and the critical found:false caveat are front-loaded, and the alternative feed approach is relevant. The description is appropriately sized, though the final sentence is somewhat dense and could be split more cleanly.

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?

For a simple read-only lookup with strong annotations and full schema coverage, the description covers the key semantics: what is looked up, what found:false means, and that no scanning occurs. It does not describe the shape of a positive verdict result, which is the main remaining gap in the absence of an output schema.

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 100%, so the schema already documents the package name, optional version, and ecosystem enum. The description reinforces that the request names a package but adds little parameter-level detail beyond the existing schema.

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 states a specific verb and resource: looking up a published catalogue verdict for an MCP server package on npm or PyPI. It also distinguishes this from scanning by saying nothing is downloaded or scanned, which separates it from the scan_* 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?

It clearly establishes the lookup context and gives an explicit alternative for matching without naming the package: downloading /api/reputation-feed.json. It also warns that found:false is not a clean result, but it does not explicitly name sibling tools or state all cases where a scan tool should be used instead.

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