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

Annotations already establish readOnlyHint and idempotentHint, so no side-effect warning is required. The description adds value by disclosing that the operation returns a list of package metadata (descriptions, latest versions, downloads), which is not present in the input schema or an output schema. It does not discuss result limits or matching semantics, but these are minor given the safety 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?

Two short sentences, front-loaded with the action and registry, then the result content. There is no filler, repetition of schema details, or unnecessary context.

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 read-only search tool with full schema coverage, the description is sufficient: required query behavior is clear, optional page and sort are documented in the schema, and the return shape is summarized because there is no output schema. Annotations cover safety and idempotency, so no hidden side-effect context is needed.

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?

All three parameters are already described in the schema, including defaults and the enum for sort. The description's 'by keyword' merely mirrors the query parameter and adds no new parameter semantics, so the baseline score of 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?

States a specific action—searching the Hex.pm registry by keyword—and specifies the result as a list of matching packages with descriptions, versions, and downloads. This is clearly distinct from sibling tools like get_package or list_releases even without naming them.

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 phrase 'by keyword' clearly identifies the intended use case: keyword-based package discovery. It does not explicitly mention alternatives like get_package for exact-name lookups or search_within, so it lacks exclusions, but the context is otherwise clear.

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