21st_magic_component_builder

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

With no annotations, the description appropriately carries the behavioral burden. It clearly discloses that the tool only returns a snippet and does not modify files, and it sets the post-call expectation to edit/add files. This is key behavioral context, though it omits details like failure modes or rate limits.

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 three sentences, each serving a distinct purpose: when to use, what it returns, and the required follow-up. It is front-loaded with the trigger conditions and contains no fluff or redundant information.

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?

The description adequately covers the tool's purpose, output scope, and the agent's next steps, which is sufficient for selecting and invoking it. It could be improved by explicitly contrasting with sibling tools or describing the snippet's format, but the provided context satisfies the core requirements.

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% (all five parameters have detailed descriptions). The tool description itself adds no parameter-specific meaning, but the baseline of 3 is sufficient because the schema already documents each parameter thoroughly, including concise search query constraints and extraction instructions.

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 clearly states the tool's function: it returns a text snippet for a requested UI component. It provides specific trigger examples (e.g., '/ui', button, dialog) and explicitly notes the tool 'ONLY returns the text snippet', distinguishing it from sibling tools that likely handle inspiration or refinement.

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?

The description gives explicit when-to-use guidance with concrete examples of user requests. It also implies exclusions via 'ONLY returns the text snippet' and instructs that file integration must happen afterward. However, it does not explicitly name alternatives or state when not to use this tool.

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