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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states that the tool returns 'top matches with descriptions' and clarifies ecosystem support, which is useful. However, it does not mention result ordering, pagination, rate limits, or error behavior. Given the absence of annotations, more behavioral detail would be beneficial, but the core behavior is clear.

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 description is two sentences, front-loaded with the core purpose and followed by a concise note on supported ecosystems. Every word contributes to the agent's understanding, with no redundancy or fluff.

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 straightforward search tool, the description is fairly complete. Combined with the fully-documented schema, the agent knows the input parameters, supported ecosystems, and output type (top matches with descriptions). Missing details like response format and pagination are minor given the tool's simplicity; the core information needed to call it correctly is present.

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?

The input schema already covers all 3 parameters with descriptions (100% coverage), so the description needs to add minimal value. It does add useful context by explaining that PyPI is excluded despite being a known registry, which clarifies the enum's restriction. This goes beyond the schema and helps disambiguate why the enum only allows npm and cargo.

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 clearly states the tool's purpose: 'Search for packages by keyword and get top matches with descriptions.' It specifies a concrete action (search), a resource (packages), and the output (top matches with descriptions). It differentiates from sibling tools (package_dependencies, package_health, etc.) which focus on specific aspects of a known package, while this is about discovery.

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?

The description explicitly names supported ecosystems (npm, cargo) and explains why PyPI is excluded ('no public search API'), which helps an agent know when this tool is appropriate and when it is not. It does not explicitly contrast with sibling tools, but the purpose is distinct enough that usage context is nearly implicit.

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