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

Annotations declare readOnlyHint=true and openWorldHint=false, so the safety profile is already covered. The description adds real behavioral value beyond that: it discloses the paginated return shape (one page of slugs), the degenerate-match behavior, and the fact that results include cloneable sections on this site.

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?

Front-loaded with the core action and return shape, then parameter notes, then the guide pointer — a sensible priority order. It is dense but almost every clause carries information; only the fallback explanation is slightly tucked away in the middle.

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?

There is no output schema, so the description must describe returns — and it does (slugs, descriptions, tags, cloneable site sections). With 15 optional parameters and full schema coverage, the remaining gaps (sort defaults are in the schema, so fine) are minor; a mention of result-count/limits would push it to 5.

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 each of the 15 parameters. The description still adds meaning: it clarifies that q expects short layout phrases ('split hero'), that categories/styles are OR-filters, and that page paginates — useful signals not spelled out as filtering semantics in 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+resource (search the block library) and instantly distinguishes itself from siblings by noting the return is 'one page of slugs with descriptions and tags (full structure: get_block).' An agent can tell it apart from get_block, list_blocks, and search_site_nodes without opening a 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?

Explicitly routes to alternatives: get_block for full structure and get_style_reference({topic:'blocks'}) as a guide. Also explains what the 'Fallback — not an exact match' case means. It stops short of stating when-not-to-use (e.g. browsing the whole library), so not a full 5.

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