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

Annotations already declare the safe read profile (readOnlyHint=true, destructive=false, openWorld=false), and the description adds real context beyond them: the ~200-result cap, category grouping, and the returned fields. It doesn't discuss pagination or ordering, but the cap implies a single bounded call, so the coverage is solid.

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?

Purpose is front-loaded in the first sentence, the sibling routing comes next, and the parameter nuance closes in a short clause. No filler, no repetition of what the schema already lists verbatim.

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 read-only, zero-required-parameter list tool with no output schema, the description covers result scope, grouping, fields, filter semantics, and the alternative tool. The only thin spot is ordering/pagination behavior, which the ~200 cap partially resolves.

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?

With 100% schema coverage the baseline is 3, but the description adds meaning by stating that the `categories`/`styles` arrays OR-match in one call, clarifying the array-vs-single interaction the schema only implies ('merged with categories'). It stops short of explaining enum values, which the schema already enumerates.

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 ('List library blocks'), gives the scope ('up to ~200'), the grouping ('by category'), and the returned fields ('slug, name, tags'). It explicitly contrasts with search_blocks ('A broad menu; search_blocks ranks and filters'), so an agent can distinguish it from its nearest sibling 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?

Names the alternative explicitly ('search_blocks ranks and filters') and frames this tool as the broad browsing menu, which tells the agent when to prefer it. It stops short of an explicit when-not clause or listing the other related siblings (get_block, list_block_nodes), so it's clear context rather than a complete routing rule.

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