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

Annotations cover the read-only, closed-world safety profile, but the description adds a trait they do not: 'Counts as a use,' i.e. a metered/billing side effect. It also discloses the return shape (lib_* ids plus displayNames), which is valuable given there is no output schema.

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?

A single dense sentence that front-loads the resource, then the return shape, then the consuming use case, and closes with the metering note. Every clause earns its place.

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 one-parameter list tool with no output schema, the description covers purpose, return values (ids and displayNames), the downstream consumer, and the usage-metering behavior. Only minor gaps remain, such as behavior on an invalid or non-library slug.

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?

Only one parameter (slug) and schema description coverage is 100%, so the schema already carries the semantics; baseline is 3. The phrase 'a library block's' marginally narrows what the slug refers to (a block, not a page/site), but adds little 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 it distinguishes itself from the nearby sibling list_blocks by scoping to nodes within one block. The cross-reference to apply_kit_block makes the boundary unambiguous.

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 names the consuming tool (apply_kit_block's contentOverrides / propOverrides) and thus implicitly states when you need it: to look up valid keys before applying an override. No explicit when-not or sibling exclusions (e.g. vs. list_blocks) are given, so it falls short of a 5.

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