A package's state

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds meaningful context about data provenance and freshness (Repology, hourly digests, Hydra last-built timestamps, forecasts like stagingNextBreaks) that goes beyond annotations, but says nothing about whether the call is expensive or how stale data can be.

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?

It is front-loaded correctly with the core purpose in the first clause, and the semicolon list does group related fields. However the whole description is a single sprawling sentence that is hard to parse, and the dense enumeration could have been shortened with a clearer hierarchy.

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, this description is the only source of return-value information, and it enumerates the returned fields thoroughly (builds, PRs, CVEs, maintainers, staging forecasts). The main gap is that it never routes the agent from find_packages to this tool or states prerequisites.

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 the schema already documents both parameters, including the attribute syntax and the python3Packages alias. The description adds no format or edge-case detail about name or repology beyond what the schema provides, so 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 opening clause states the resource precisely ('one nixpkgs package') and the scope ('everything nixkeeper knows'), which an agent can distinguish from aggregate siblings like overview or needs_attention. It never names a verb (get/fetch/detail), but the lookup intent is unambiguous from the description and the single required name parameter.

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?

There is no explicit when-to-use guidance and no sibling is named as an alternative. The reader must infer that find_packages searches while this one details a single package; the relationship is never stated.

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