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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds that the operation returns specific fields (description, licenses, links, latest version, download counts), but it doesn't disclose behavior on missing packages or any other runtime traits. This adds some value without contradicting the 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 description is a single, front-loaded sentence with zero wasted words. It states the action, the target, and the exact return payload, all before any filler.

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 one required parameter and no output schema, the description covers the essential context: the resource type, the lookup key, and the returned fields. Nothing an agent needs to successfully call it is missing.

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% and the single parameter 'name' is described with examples. The description adds context about what the package name refers to (Hex.pm, Elixir/Erlang), but that's more tool-level context than parameter semantics. Baseline 3 is appropriate since the schema already fully documents the parameter.

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 ('Look up') with a specific resource ('a single Hex.pm package ... by name'), clearly distinguishing it from sibling search/list tools like search_packages. It also names the target ecosystem (Elixir/Erlang mix) which removes ambiguity.

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 'a single ... by name' implies this should be used when the exact package name is known, which differentiates it from search_packages or list_releases. However, it doesn't explicitly name alternatives or state when not to use it, so it stops short of full guidance.

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