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

With no annotations, the description carries real weight: it discloses that the data comes from a public registry JSON (read-only, no mutation), that the caller's OpenAny gateway credentials are used, and that charges and authorization are governed by the gateway — a cost-relevant trait an agent should know before calling. It does not address behavior on unknown package names or whether errors are billed, which keeps it below a 5.

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?

Three sentences, front-loaded with what is returned, then the parameter mapping, then credential/cost context. The second sentence largely duplicates schema content, which is minor waste, but nothing else is padded.

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 one-parameter read tool with no output schema, the description substitutes effectively by listing the row's fields, plus notes gateway credential handling and the crates-only downloads limitation. The only remaining gaps (not-found behavior, exact price) are covered in the schema's own body description.

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% and the nested body already documents both fields, including the npm/pypi/crates enum and 'default npm'. The description's restatement of `ecosystem` and `name` adds no syntax or format meaning beyond the schema, so the baseline 3 applies.

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 concrete resource (one package's metadata from its registry's public JSON) and enumerates the returned fields — version, publish date, license, homepage, repository, downloads, dependency count. It is unambiguous what this fetches and no sibling (Medium posts, Steam app, Shopify products, etc.) overlaps. It stops short of naming an alternative, so it is clear but not fully sibling-differentiated.

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?

When-to-use is only implied by the subject matter (fetch facts about a package you already know the name of). The single explicit rule is the scoping constraint 'downloads (crates.io only)'. There is no statement of when not to use it, no prerequisites, and no pointer to any alternative for related lookups.

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