21st_magic_component_inspiration

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

With no annotations, the description carries the behavioral disclosure burden. It states that no code is generated, that only the text snippet is returned, and that the agent must edit or add files afterward. It does not cover authentication, limits, or exact return shape, but the key behavioral constraints are disclosed.

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 short and front-loaded with the trigger conditions. There is some redundancy between 'returns the JSON data' and 'ONLY returns the text snippet', but the overall structure is efficient and the post-call instruction earns its place.

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 two-parameter fetch-like tool with a rich schema and no output schema, this description provides sufficient context: when to use it, what it returns, what it does not do, and what the agent must do afterward. It could be slightly richer on output formatting, but it is largely complete.

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?

The input schema already documents both required parameters with 100% coverage, so the description adds limited semantic value beyond the schema. The description clarifies that searchQuery is for finding a matching UI component, but this is also reflected in the schema's parameter description.

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 identifies the action as fetching component data and previews from 21st.dev, and it contrasts itself with code generation by stating it does not generate new code. It does not explicitly distinguish itself from the refiner sibling, so it stops short of full differentiation.

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 opens with explicit trigger conditions: 'when the user wants to see component, get inspiration, or /21st'. It does not provide when-not guidance or name alternative tools, but the usage context is clear enough for an agent to select this tool appropriately.

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