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

Annotations already declare readOnlyHint=true, openWorldHint=false, and destructiveHint=false, so safety is covered structurally. The description adds a behavioral trait not present in annotations: 'Counts as a use,' a quota/billing consequence that is genuinely useful for an agent deciding whether to call it.

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 sentence plus a short trailing clause; the resource and its purpose are front-loaded, and the quota note is kept to three words. No wasted prose.

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 carries the burden of describing returns and does so (node ids and displayNames). It is complete enough to invoke correctly, though it doesn't state whether all nodes are returned or mention any size/pagination limit.

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 slug parameter is documented in the schema, so the baseline is 3. The description only implies the slug refers to a library block (via 'a library block's node ids') and adds no format or syntax detail beyond the schema.

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 (List) and resource (a library block's node ids and displayNames), and names the concrete artifact returned (lib_* keys). It also distinguishes itself from the sibling list_blocks by scoping to a single block's nodes and tying the output to apply_kit_block's override keys.

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?

It frames the output's purpose — the keys feed apply_kit_block's contentOverrides/propOverrides — which tells the agent when this tool is needed. It does not explicitly say 'call this before apply_kit_block' or state when not to use it, so it stops short of full when/when-not guidance.

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