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

Annotations only declare readOnlyHint=true, and the description adds real behavioral context beyond that: the data is a served snapshot (no live GitHub API), staleness is signalled via asOf stamps, and unknown repos return "not-in-library." It doesn't cover rate limits or caching, but the important data-provenance caveat is present.

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 sentences, no filler, with the core resource and returned fields front-loaded and the dataset-provenance caveat placed second where it qualifies the whole result.

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?

An output schema exists and annotations cover safety, so the description needn't restate return shapes; it still gives enough about field set, data source, freshness, and the failure case for correct selection and invocation.

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 both parameters are already documented; the description still adds meaning by noting the description comes back keyed by locale codes across up to 16 UI languages, which clarifies the behavior of the lg enum beyond the schema's one-line note.

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 verb and resource ("Library record for one repository") and enumerates the fields returned, which lets an agent distinguish it from list/search siblings like search_library. It stops short of explicitly contrasting with get_repo_history (current snapshot vs. history), so sibling differentiation is only partially achieved.

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?

Usage is implied by the required owner/name lookup and the note that results come from the local dataset rather than a live GitHub call. The not-in-library case is disclosed, but there is no explicit guidance on when to prefer this over get_repo_history or search_library.

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