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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real context beyond that: the ~200 result cap and the category grouping of results. No auth or pagination details, but coverage is good for a read-only listing tool.

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?

Two short sentences, front-loaded with purpose, scope and return shape before the sibling comparison. Slightly terse/telegraphic phrasing, but no wasted sentences.

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 list tool with four fully-documented optional params and no output schema, the description supplies result cap, grouping and the key result fields, which is enough to call it correctly. Minor omission: it doesn't say what happens when no filters are supplied.

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 description coverage is 100%, so the baseline is 3. The clause 'categories/styles arrays OR-match in one call' clarifies combination logic, but the schema already states 'OR-filter by several categories'; the description adds little beyond it.

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 (library blocks), adds scope (~200 cap) and return shape (grouped by category: slug, name, tags), and explicitly positions itself against the search_blocks sibling. An agent can distinguish list vs. search 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?

Contrasts the two tools directly: this one is 'a broad menu' while search_blocks 'ranks and filters'. That gives both the when-to-use and the alternative to prefer for ranked/filtered results.

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