check_library

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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so safety is covered. The description adds genuinely useful context beyond that: the data sources (React Native Directory, NativeKeel's compatibility table) and the coverage caveat 'where NativeKeel has a compatibility table', which warns results may be partial.

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?

One front-loaded sentence with a colon introducing a scannable list of returned facts; no filler or repetition. It is dense and long-ish for a single sentence, but every clause carries content.

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, the description must carry the return-value burden, and it does so by enumerating the fields returned plus the caveat about compatibility-table coverage and the no-version case. It stops short of stating result format or how missing data is surfaced, but an agent has enough to call it correctly.

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 both parameter descriptions already explain the npm package name format and that react_native is optional with only general facts returned otherwise. The description restates the react_native purpose ('the version range that works with a given React Native version') but adds no syntax or format detail beyond the schema, so the 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?

States a specific verb and resource ('check_library' → what to know about one React Native library) and enumerates the exact facts returned: latest version, New Architecture support, maintenance status, compatibility range, replacements, known traps. This is clearly distinguishable from siblings like upgrade_plan or verify_upgrade without opening either schema.

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 'before adding or upgrading it' gives a concrete decision point for invoking the tool, which is more than implied usage. It does not name an alternative (e.g., upgrade_plan) or state when not to use it, so it falls short of full routing guidance.

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