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

Annotations already declare readOnly, idempotent, and non-destructive, so the description adds useful context about exact-name matching and the shape/counts of results. It discloses that results carry dependentReposCount, dependentPackagesCount, and vulnerabilityCount, which supplements the schema. No contradictions with 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?

Three sentences, front-loaded with the core action, and every sentence adds value: scope, exact-match behavior, narrowing option, and result contents. No filler or redundancy.

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 no output schema, the description adequately explains the return shape (normalized package with counts) and the key behavior. It covers exact matching, cross-registry scope, optional ecosystem filtering, and result fields, making it complete for context.

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 meaningful examples (q=react) and clarifies each result is a normalized ecosystemsPackage with reverse-dependency counts. It enriches understanding of q and ecosystem beyond the schema definitions.

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 uses a specific verb phrase ('Look a package name up across 50+ registries at once') and clearly identifies the resource (ecosyste.ms) and scope. It distinguishes itself from siblings by emphasizing exact-name lookup across many ecosystems, which is unique among the listed tools.

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 provides clear context for when to use the tool (cross-registry lookup) and explicitly notes it is exact-match, not fuzzy full-text, which helps choose over sibling search tools. It also explains how to narrow results with the ecosystem parameter, though it does not explicitly name alternative tools.

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