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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description adds meaningful behavioral context by explaining that each block is a TSX file and an SCSS file meant to be copied and changed, which tells the agent what to expect from the results. It does not describe pagination or listing limits, but with annotations and a simple schema this is a minor gap.

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?

The description is two sentences with no wasted words: the first explains what blocks are, and the second gives a clear usage directive. It is appropriately sized for a simple listing tool and front-loads the conceptual framing before the action cue.

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?

Given the low complexity, read-only annotations, and full schema coverage, the description is nearly complete. It explains what blocks are and when to use the tool, so an agent can invoke it correctly. The only missing detail is an explicit statement that it lists all blocks and optionally filters by category, but the schema covers the filter.

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%, and the only parameter (category) is fully documented with its allowed values in the schema itself. The description does not add any additional meaning about the category parameter, such as filtering behavior or default scope, so the baseline of 3 applies.

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?

The description defines what blocks are and signals a discovery use case, making it clear this tool is for finding pre-built screens/parts. However, it does not explicitly state that it lists blocks or that it can filter by category, relying on the tool name and title for the exact action. It distinguishes itself from siblings like get_block by focusing on browsing available blocks rather than retrieving one.

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 gives clear context for when to use the tool: 'Look here before building a screen from nothing.' This is a strong, actionable usage cue. It does not mention when not to use it or explicitly point to alternative tools like list_components or search_docs, 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.